
Oass-JjclB SS 
Book. — *Syg 



COPYRIGHT DEPOSIT 



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GEOLOGY 

By Thomas C. Chamberlin and Rollin D. Salisbury, 

Professors in the University of Chicago. {American 

Science Series.) 3 vols. 8vo. 

Vol. I. Geological Processes and Their Results. 

Vols. II and III. Earth History. (Not sold separately.) 

A COLLEGE TEXT-BOOK OF GEOLOGY 

By Thomas C. Chamberlin and Rollin D. Salisbury. 
{American Science Series.) 8vo. 

PHYSIOGRAPHY 

By R. D. Salisbury. (American Science Series.) 8vo. 
The same. Briefer Course. i2mo. 
The same. Elementary Course. i2mo. 

ELEMENTS OF GEOGRAPHY 

By Rollin D. Salisbury, Harlan H. Barrows and 
Walter S. Tower, of the Department of Geography, 
The University of Chicago. (American Science Series.) 
i2mo. 

MODERN GEOGRAPHY 

By Rollin D. Salisbury, Harlan H. Barrows and 
Walter S. Tower, of the Department of Geography, 
The University of Chicago. (American Science Series.) 
i2mo. 



HENRY HOLT AND COMPANY, Publishers 
New York and Chicago 



AMERICAN SCIENCE SERIES. 



MODERN GEOGRAPHY 

FOR HIGH SCHOOLS 



BY 

ROLLIN D. SALISBURY 
HARLAN H. BARROWS 

AND 

WALTER S. TOWER 

Of the Department of Geography, the University of Chicago 




NEW YORK 

HENRY HOLT AND COMPANY 

1913 



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Copyright, 1913 

BY 

HENRY HOLT AND COMPANY 



STfje ILakrstUe $rrss 

R. R. DONNELLEY & SONS COMPANY 
CHICAGO 

©CU343148 

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PREFACE 

For several years there has been a widespread demand for a 
course in general geography in high schools. This book is designed 
to serve as the basis for such a course. All rational work in general 
geography must be founded on physiography, and this fact has 
determined the organization of the material of this book. Physi- 
ographic processes and features are treated briefly, however, while 
their relations to life, and especially to human affairs, are developed 
at greater length. The book has been prepared with the conviction 
that the chief object in geography teaching should be preparation 
for everyday life, for citizenship in the widest sense. Hence the 
authors constantly have sought (i) to make the text explanatory 
rather than merely descriptive, so that it may afford training in clear 
thinking; and (2) to emphasize the relations of earth, air, and water 
to man's activities and interests, so that the knowledge gained may 
be directly useful. 

The principles developed have been applied at greatest length 
to the United States, because this country is of most interest and 
importance to American students. Furthermore, space forbade the 
application of these principles in detail to other countries. 

The larger aspects of economic and commercial geography are 
covered in connection with such topics as soils, minerals, waterways, 
water power, harbors, and the distribution and development of 
industries and cities. It is hoped, therefore, that the book may be 
found useful by teachers of commercial geography, as well as by those 
who have sought to " humanize" high school physiography. 

The illustrations are intended to serve as the basis for classroom 
discussions and quizzes, and should be studied and interpreted as 
carefully as the text itself. The questions may be used for written 
work or for classroom discussion. The answers to most of them are 
not to be found in the text, but can be reasoned out by students who 
have followed the text with understanding. The physical maps at 
the end of the book afford the means of locating most of the places 
and features mentioned in the text. 



vi PREFACE 

Teachers using this book will find it helpful to have the authors' 
Elements of Geography. The larger volume discusses in greater 
detail many of the topics of this one, and gives numerous references 
to supplementary material. A list of books on geography and related 
subjects which might well be in a high school library is given at the 
end of this book. 



CONTENTS 



CHAPTER 

I. 

II. 



III. 



PAGE 



IV. 



VI. 



VII. 



vin. 



IX. 



x. 



The Nature of Geography 
Earth Relations 

The Solar System 

The Earth as a Planet 

Maps and Map Reading 

Terrestrial Magnetism 
Relief Features of the Earth 

Relief Features of the First Order . 

Relief Features of the Second Order 

Subordinate Topographic Features 

Comparison of the Continents 
The Nature and Functions of the Atmosphere 

General Conceptions .... 

Composition . .... 

Relations of the Different Constituents to Life 
Climatic Factors: Temperature . 

General Conslderations ' . 

Seasons . 

Relation of Temperature and Altitude 

Representation of Temperature on Maps 

Ranges of Temperature 
Climatic Factors: Moisture 

Importance of Atmospheric Moisture 

Evaporation ..... 

Humidity ..... 
Climatic Factors: Pressure and Wind 

Pressure ..... 

Representation of Pressure on Maps and Charts 

Winds ..... 

Winds and Rainfall 
Storms and Weather Forecasting 

Weather Maps 

Cyclones and Anticyclones . 

Weather Forecasting . 

Local Storms 
Tropical Climate 

General Characteristics of Tropical Climates 

Types of Climate Within the Tropics 

The Future of the Tropics . 
Types of Climate in the Temperate (Intermediate) Zones 

General Characteristics of Climates of the Temperate 
Zones . . 

Types of Climate 



4 
4 
5 

15 
18 
19 
19 

21 
23 

24 
27 
27 

28 

29 
34 
34 
4i 
44 
45 
52 
56 
56 
56 
59 
66 
66 

67 

72 

76 

81 

81 

85 

93 

95 

98 

98 

101 

112 

113 

114 
117 



Vlll 



CONTENTS 



XI. Climate of Polar Regions . 
General Considerations 
The Antarctic Region . 
The Arctic Regions 
XII. The Oceans 

General Considerations 
Temperature of the Sea 
Movements of Sea-Water 
The Life of the Sea 

XIII. The Materials of the Land and Their Uses 

General Constitution . 

Soils .... 

Mineral Products and Their Uses 

Conservation of Mineral Resources 

XIV. Changes of the Earth's Surface Due to Internal Forces 

Slow Crustal Movements .... 

Earthquakes 

Vulcanism ....... 

XV. Modification of Land Surfaces by External Agents 

The Work of the Wind .... 

Ground-Water 

The Work of Streams . . 

The Work of Ice 

XVI. The Uses and Problems of Inland Waters 

Navigation 

Water Power ...... 

Irrigation ....... 

Reclamation of Swamp and Overflowed Lands 

Water Supply 

XVII. Mountains and Plateaus and Their Relations to Life 

Mountains 

Plateaus ........ 

XVIII. Plains and Their Relations to Life .... 

Life in Well-Watered Plains of Muddle Latitudes 

Life in Semi-Arid Plains 

Life in Arid Plains ...... 

Life in Arctic Plains ...... 

Life in Humid Plains of Low Latitudes 
XIX. Coast-Lines and Harbors ...... 

XX. Distribution and Development of the Leading Industries 
of the United States .... 

Agriculture . . . . . 

Forest Resources and Lumbering 

The Fishing Industries .... 

Mining, Quarrying, Etc. .... 

Manufacturing Industries .... 
XXI. Distribution of Population; Development of Cities 

Factors Affecting Density .... 

Cities 399 



LIST OF PLATES 



AT END OF VOLUME 



Plate I. 
Plate II. 
Plate III. 
Plate IV. 
Plate V. 
Plate VI. 
Plate VII. 



North America 

United States 

South America 

Europe 

Asia 

Africa 

Australia 



IX 



MODERN GEOGRAPHY 



CHAPTER I 
THE NATURE OF GEOGRAPHY 

Ancient and modern geography. Geography has been studied 
since ancient times, for people always have wanted to know about 
the earth on which they lived; but the conception of geography has 
changed greatly as years have gone by. In olden times it was re- 
garded as a description of the earth. It included an account of 
the countries into which the earth is divided, their physical features, 
such as rivers, mountains, and plains, and their inhabitants and 
products. Modern geography is concerned especially with the 
effects of physical features, such as land forms, water, and climate, 
on living things. 

Divisions of geography. It is clear that there are two main 
parts to the study of geography: (i) The physical features of the 
earth (land, water, air) which affect life; and (2) the ways in which 
different forms of life respond to their physical surroundings. 

Various groups of physical phenomena may be the subjects of 
special study. Thus the phenomena of the atmosphere are considered 
in meteorology and climatology; those of the waters in oceanography 
and hydrography; and those of the lands in physiography, as some 
would define that term. Similarly, earth relations to life may be 
studied with special reference to plants {plant geography), to animals 
{animal geography), or to man {human geography). 

Relations to other subjects. The study of these different 
phases of geography brings it into contact with many other sciences. 
The form, size, and motions of the earth are matters of astronomy 
as well as geography; the origin and characteristics of land forms 
and the distribution of useful minerals are matters of geology as well 
as geography; the effects of physical conditions on plant and animal 



2 THE NATURE OF GEOGRAPHY 

life are phases of botany and zoology as well as geography; the distri- 
bution of mankind, man's subdivision of the earth into political 
units, and many other matters, relate geography closely to history; 
and man's present activities, influenced by geographic conditions, 
are factors of political economy. 

Importance of human geography. Most interest attaches to the 
study of the earth in its relations to man. Human activities are so 
many and varied, and are influenced in so many ways by physical 
conditions, that special study often is made of related effects. Thus 
economic geography traces the influence of natural factors in the pro- 
duction of things useful to man. The relations of land forms, soil, 
and climate to the raising of crops is an example. Commercial 
geography considers the influence of natural factors in the transporta- 
tion and exchange of various commodities, as the trade in tropical 
fruits between warm regions and those too cold to raise them. His- 
torical geography is concerned with the influence of physical condi- 
tions on past events. Political geography traces the influences of lo- 
cation, topography, climate, and natural resources on the develop- 
ment of countries. 

The basis of other studies. Since geography shows the many 
ways in which the earth is related to the life of man, it is important 
as the basis of many other studies. It is especially important in 
connection with the study of history, for in all ages the conditions 
under which people lived have influenced their occupations, their 
stage of development, and their relations to the rest of the world. 
The better geography is understood, therefore, the easier it is to under- 
stand the meaning of historical events. The Jews in Palestine never 
became seamen because the nearest coast had no good harbors, 
while their neighbors, the Phoenicians, on a more favorable coast, 
were the first good sailors, and for many years were influential in 
Mediterranean districts outside their own country. Russia has 
striven for more than two centuries to secure satisfactory seacoasts, 
and as a result has been led into several wars with her neighbors. 
Great Britain, difficult to invade because an island, was able at 
an early date to use her natural resources to great advantage, and 
became the leading nation of the world in manufacturing and com- 
merce. In our country, slavery developed chiefly in the South, 
mainly because the conditions of field labor there favored it more than 
in the North. These examples suggest the close connection between 
geography and some important facts and phases of history. 



EARTH CONDITIONS AND LIFE 3 

Geography is related no less intimately to present events. The 
distribution of people over the face of the earth, the manner in which 
they live, and their grouping in countries and cities always bear some 
relation to earth conditions. Many old cities, like Venice, were 
located where defense against invasion was easy. Most new cities 
were located with respect to natural advantages for manufacturing 
or commerce. Food, dress, shelter, occupations, industries, prod- 
ucts, trade, and many other facts and conditions of life are in- 
fluenced by physical surroundings. Deserts have little vegetation 
and few animals, for water is scarce. Since man depends on plants 
and animals for food and clothing, and largely also for shelter, desert 
populations are small. 

Tropical natives wear little clothing and eat little meat, largely 
because bodily temperatures are maintained easily without either. 
They have little commerce, because their wants are few. The 
people of middle latitudes, on the other hand, must adapt them- 
selves, in the matter of food, clothing, and shelter, to extremes of 
heat and cold. Their wants are therefore many and varied. Com- 
plex industries and world commerce are needed to satisfy them. 
The United States is the greatest producer of foodstuffs, because of 
the great extent of favorable surface, soil, and climate — resources 
which a progressive people have used to advantage. Several coun- 
tries of western Europe have advantages for extensive manufacturing, 
such as supplies of coal near good seaports; but they cannot produce 
all the raw materials needed for their factories, nor all the food for 
their factory workers. Hence large quantities of raw materials and 
food, like cotton and copper, flour and meat, are exported yearly 
from the United States to these European countries. 

An understanding of the larger relations between physical con- 
ditions and life in general is necessary for an understanding of the 
effects of the physical surroundings of man on his interests and 
activities. This in turn helps one to understand the affairs of the 
world, and therefore is important to good citizenship. 



CHAPTER II 
EARTH RELATIONS 

The Solar System 

Members of solar system. The solar system includes the sun 
and all the bodies which revolve about it (Fig. i). There are eight 
planets, of which the earth is one. To us, all the planets except our 
own appear as stars, but in their motions they differ from other 
stars. Commencing with the nearest to the sun, the planets are, 




Fig. i. Diagram of the principal members of the solar system. The size 
of the bodies is exaggerated greatly as compared with that of the sun and the 
orbits. The central body is the sun; the others are the planets. 

in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, 
and Neptune. All but Mercury and Venus have satellites correspond- 
ing to our moon. Saturn has nine of them. 

Besides the planets and their satellites, the solar system includes 
numerous other bodies (mostly asteroids) which have little influence 
on the earth. 

The sun is more than i ,000,000 times as large as the earth, and 
very hot. From it the earth receives nearly all its heat and light. 
The other planets shine only by reflected sunlight. 

Beyond the great system to which the earth belongs there are 
many thousands of stars, each of which may be compared to our 
sun, though many of them are vastly larger. 

The planets. The planets are all of similar form, all rotate on 
axes, and move in nearly circular paths about the sun in the same 
direction, but they are strikingly unlike in some respects. Jupiter, 

4 



THE FORM OF THE EARTH 



5 



the largest, has a diameter more than ten times that of the earth, 
while the diameter of Mercury, the smallest planet, is only about one- 
third that of the earth. The innermost planet revolves about the 
sun in 88 days, the outermost in 165 years. The shortest rotation 
period of a planet is less than 10 hours, while that of Venus is nearly 
225 days. From the standpoint of life, the earth is the most favored 
of the planets. Indeed, the conditions of heat and light would prevent 
the existence of such life as we know on most of the other planets. 

The Earth as a Planet 

Form. The form of the earth is very much like that of a sphere, 
but since it is not exactly a sphere, it is called a spheroid. The form 
has been determined in various ways: (1) Ships have sailed around 
it. This proves that it is everywhere bounded by curved surfaces, 
but it does not prove that it is a sphere or even a spheroid, for it would 
be possible to sail around it if it had the shape of an egg. (2) When 
a vessel goes to sea, its lower part disappears first, and when a vessel 
approaches land, its highest part is seen first from the land. By 
people on the vessel, the highest lands are seen first, and the low 
ones later; the spires and chimneys of buildings appear before the 
roofs, and the roofs before the lower parts. Like (1) above, these 
facts show only that the earth has a curved surface. But from 
whatever port vessels start, and in whatever direction they sail, 
objects on land disappear at about the same rate. This means that 
the curvature of the surface is nearly the same in all directions. A body 
whose curvature is the same in all directions is a sphere, and a body 
whose curvature is nearly the same in all directions is nearly a sphere. 
(3) Again, the earth is sometimes between the sun and the moon. It 
then casts a shadow on the moon (making an eclipse), and this shadow 
always appears to be circular. In these and other ways it is known 
that the form of the earth does not depart greatly from that of a 
sphere. (4) That the earth is not exactly round, however, is shown in 
various ways. For example, a body weighs slightly more in high 
latitudes than in low latitudes. This means that it is nearer the 
center of the earth in the high latitudes than in the low; or, in other 
words, that the earth is not a true sphere. (5) Certain mathematical 
calculations not given here (for one of them, see p. n) prove that the 
curvature of the earth's surface is less in high latitudes than nearer 
the equator. 



6 EARTH RELATIONS 

Consequences of the earth's form. The spheroidal form of the 
earth facilitates travel and transportation. It aids commerce in 
another important way. The attraction of the earth causes bodies 
to have weight. Because the earth is nearly round, gravity is nearly 
equal everywhere upon its surface, and, as we have already seen, the 
weight of a given object is therefore nearly constant. If the weight 
of things varied greatly from place to place, this variation would 
interfere seriously with trade between different parts of the world. 

Size. The circumference of the earth is nearly 25,000 miles, 
and its diameter nearly 8,000 miles. Since the earth is not a perfect 
sphere, its various diameters and circumferences are not exactly 
equal. Its longest diameter is 7,926.5 miles and its shortest nearly 
27 miles less (7,899.7 miles). The area of the earth's surface is 
nearly 197,000,000 square miles. 

Motions 

The earth has two principal motions : (1) It rotates on its shortest 
diameter, called its axis, and (2) it revolves around the sun. The 
axis is an imaginary line, and its ends are the poles. The circumfer- 
ence midway between the poles is the equator. 

Rotation. The rotation of the earth from west to east gives us 
day and night, for one side of the earth and then the other is turned 
toward the sun during each rotation. The time of rotation, about 
24 hours, determines the length of a day (day and night). 

Human activities are in general adjusted to the turning of the 
earth, the succession of daylight and darkness affording convenient 
intervals for work and rest. In those parts of the earth where the 
intervals of light and of darkness are many days (instead of hours), 
this habit of regularity of work and rest is less general. During 
the long period of light, the hunting people of Greenland, for example, 
cease their work or seek rest only when fatigue overtakes them. 
During the long period of darkness they have no regular work or exer- 
cise, and are much less vigorous than in the period of light. The 
long " night " ot polar regions is very trying to the health and strength 
of people accustomed to a period of light each day. 

The period of rotation furnishes also a natural unit for measuring 
time. Again, the rising and setting of the sun, due to the earth's 
rotation, give us a simple system of directions. 

Revolution. The earth revolves about the sun in a little more 
than 365 days, and the period of revolution fixes the length of the year. 



MOTIONS OF THE EARTH 7 

The path of the earth around the sun is its orbit. The orbit of the 
earth is not a circle, but a curve called an ellipse (Fig. 2), and the 
distance of the earth from the sun varies from time to time. When 



Perihelion 




Aphelion 



Fig. 2. The orbit of the earth is an ellipse, with the sun in one of the foci. 

the earth is nearest the sun {perihelion), the distance between them 
is about 3,000,000 miles less than when they are farthest apart 




JUNE 21 








^^ 




Fig. 3. Diagram showing the position of the earth with reference to the sun 
at the solstices and equinoxes, and the inclination of its axis. 



{aphelion). The earth is nearest the sun (about 91,500,000 miles) 
in the early part of the winter of the northern hemisphere (about 
January 1st), and farthest from it (about 94,500,000 miles) early in 
the summer. The motion of the earth through space during its 



8 



EARTH RELATIONS 



revolution about the sun is at the rate of about 600,000,000 miles a 
year, or more than 1,100 miles each minute. 

The earth's axis is inclined toward the plane of its orbit about 
2^/2 degrees (Fig. 3). This position of the axis, together with 
the motions of the earth, has much to do with the distribution of 
the heat and light received from the sun, with the changes in the 
length of day (daylight) and night, and with the seasons.. 

Latitude, Longitude, and Time 

Latitude. The equator has been denned as the circle about 
the earth midway between the poles. Circles parallel to the equa- 
tor are parallels. The number of parallels which might be drawn 
is very large, though only a few are represented on maps. The 
length of parallels varies greatly, those near the equator being longer, 





Fig. 4. Parallels and meridians. 



and those near the poles shorter. The north and south lines that 
pass from pole to pole on the earth's surface are meridians. All 
meridians come together at each pole. 

A few meridians and parallels appear in Fig. 4, which shows 
the earth in two positions. The left-hand part of the figure shows 
the half of each parallel represented and the whole of each meridian. 
The right-hand part shows the relation of parallels to the North 
Pole. The distance between the equator ^nd either pole is divided 
into 90 parts, called degrees (written 90^. Each degree is divided 
into 60 parts, called minutes (60') . Each minute is divided into 
60 parts, called seconds (60"). Distance north or south of the equa- 
tor may therefore be determined from a globe or map by means of 
parallels. The system of parallels and meridians is made possible 
by the form of the earth and its rotation on its axis. 



LOCATION OF PLACES ON THE EARTH 



North Pole 



Distance north or south of the equator is called latitude. North 
latitude is north of the equator, and south latitude is south of it. The 
degrees, minutes, and seconds are numbered from the equator toward 
the poles. The latitude of the equator is o°. Latitude i° N. is one 
degree north of the equator,- and latitude 90 N. is at the North Pole. 
Latitude i° S. is one degree 
south of the equator, and lati- 
tude 90 S. is at the South Pole. 

Longitude. Position on a 
parallel is indicated by means 
of the meridians which cross it. 
The number of possible merid- 
ians is very great, but, as in 
the case of parallels, only a few 
are commonly shown on maps. 
One meridian, that passing 
through Greenwich, England, 
where the British Royal Obser- 
vatory was established in 1675, 
is usually chosen as the merid- 
ian from which distances east 
and west are reckoned (Fig. 5). 
This meridian is the meridian 
of o°, and is sometimes called 
the prime meridian. Distance 

east or west of this meridian is known as longitude. Places east of 
longitude o° are in east longitude, and those west of it are in west longi- 
tude. East and west longitude respectively are regarded as extending 
180 from the meridian of o°; that is, half-way around the earth. 

The position of a place on the earth 's surface may be fixed exactly 
by means of meridians and parallels. If a place is in longitude 30 
E., its distance east of the meridian o° is known. If at the same 
time it is in latitude 30 N., it must be on the parallel of 30 N. where 
it is crossed by the meridian of 30 E. So convenient and accurate 
is this method of locating places and reckoning distance, that parallels 
and meridians are used in many places as boundaries between states, 
counties, and townships. 

The poles are the only places which have latitude but no longitude. 
Since all meridians come together at the poles, the poles cannot be 
said to lie either east or west of the meridian of Greenwich. At the 




South Pole 



Fig. 5. Diagram showing the position 
of the axis of the earth, the poles, the 
equator, the meridian of Greenwich, and 
the meridian of 180 . 



IO 



EARTH RELATIONS 



North Pole the only direction is south, and at the South Pole the only- 
direction is north. 

Longitude and time. There is a definite relation between 
longitude and time. Since the earth turns through 360 in 24 hours, 
it turns 15 in one hour, and 15' of longitude in one minute of time. 
The sun therefore rises one hour earlier at a place in longitude o° 
than at a place in the same latitude in longitude 15 W., and one 



4 lr - 




Fig. 6. Map showing standard time belts of the United States in Dec., 191 2. 



hour later than at a place in the same latitude in longitude 15 E. 
Similarly, noon comes an hour earlier in longitude o° than in longitude 
1 5 W., and an hour later than in longitude 15 E. All places on a 
given meridian have noon at the same time and midnight at the same 
time, and such places are said to have the same time; but places on dif- 
ferent meridians have different times. St. Louis is about 15 farther 
west than Philadelphia, and Denver is about 15 west of St. Louis. 
When it is noon at Philadelphia it is about eleven o 'clock at St. Louis 
and ten at Denver. When it is one o 'clock at Philadelphia it is noon 
at St. Louis and eleven o'clock at Denver, and when it is noon at 
Denver it is one o 'clock at St. Louis and two at Philadelphia. 

The variations of time with changes of longitude become apparent 
when long journeys are made either east or west. Thus a watch which 



STANDARD TIME BELTS n 

has the correct time in New York has not the correct time when it is 
carried to Chicago. To avoid the difficulties of time-keeping growing 
out of travel, the railroads of the United States have adopted a sys- 
tem of standard time. Under this system the country is divided into 
north-south belts of convenient width (Fig. 6), and in each belt all 
railways use the same time. The railway time in adjacent belts 
differs by one hour. By this system, clocks and watches do not show 
correct local time except on one meridian of each belt. The irregular 
boundaries of the belts are due to the adoption of the nearest impor- 
tant railway points as the places for changing time on east and west 
journeys. 

Lengths of degrees. The length of a degree of longitude, as 
measured on the surface of the earth, is the V360 part of a parallel. 
Since the parallels are very much shorter near the poles than near 
the equator, the length of a degree of longitude is less in high than in 
low latitudes. At the poles, where the length of the parallel becomes 
zero, the length of a degree of longitude also becomes zero. At the 
equator, a degree of longitude is a little more than 69 (69.16) miles. 

Degrees of latitude are measured on meridians. They also vary 
in length. The length of a degree of latitude is about 68^ miles 
in India, while in Sweden, the most northerly place where a degree 
has been measured, it is 69X miles. All measurements which have 
been made show that the length of a degree of latitude, measured 
on the earth's surface, increases as the poles are approached. At 
the poles it is calculated that it must be about 69^ miles. In the 
United States, the average length is about 69 miles. The increase 
of length of the degree toward the poles means that the earth is 
flattened there. This means that the earth is a spheroid. 

Inclination of Axis and its Effects 
The sun's rays illuminate one-half of the earth all the time. 
The border of the illuminated half is called the circle of illumina- 
tion (Fig. 7). All places on one side of the circle of illumination have 
day, while all places on the other side have night. If the axis about 
which the earth rotates were perpendicular to the plane in which 
the earth revolves about the sun, the circle of illumination would 
always pass through the poles. Under these conditions, half of the 
equator and half of every parallel of latitude would be illuminated 
all the time, as in Fig. 7. If the half of each parallel were always 
illuminated, the days and nights would be equal everywhere, for it 



12 



EARTH RELATIONS 




takes just as long for a place at A (Fig. 7) to move to B (six hours, 
half of a twelve-hour day) as for it to move from B to A' (half of a 
twelve-hour night). Since days and nights are not equal at all sea- 
sons in most parts of the earth, it proves that the axis on which 

the earth rotates is not per- 
pendicular to the plane of 
its orbit. 

Again, if the earth rotated 
on an axis perpendicular to 
the plane of its orbit, the 
sun always would be equally 
high at any given place at 
the same hour of the day. 
But this is not the case. In 
the United States, for exam- 
ple, the sun is much higher 
above the horizon at noon 
in summer than in winter. 
The same is true in all lati- 
tudes similar to those of the 
United States. 

This variation of the an- 
gle at which the sun's rays 
strike the same place at dif- 
ferent times, as well as the unequal lengths of days and nights in 
most places, is the result of the inclination of the axis on which the 
earth rotates as it revolves around the sun (Fig. 3). The position 
of the axis is constant throughout the year. The effect of the 
inclination of the axis is illustrated by Fig. 3, which represents the 
earth in four positions in its orbit. On March 21st, the half of each 
parallel (the half toward the reader) is illuminated. At this time, 
therefore, days and nights are equal everywhere. On June 21st, 
more than half (the part not shaded) of every parallel of the northern 
hemisphere is illuminated, and there the days are more than 12 hours 
long and the nights correspondingly less. In the southern hemisphere 
the nights are longer than the days. On September 2 2d, the days and 
nights are again equal everywhere, for the circle of illumination 
divides every parallel into two equal parts. In the figure, the lighted 
part is away from the reader. On December 2 2d, more than half of 
each parallel in the southern hemisphere is in the light, and there the 



Fig. 7. Diagram to illustrate the fact that 
half of the earth is lighted by the sun at any 
one time. The parallel lines at the right 
show the direction of the sun's rays. The 
part of the earth not shaded is lighted by 
the sun; the other half is in darkness. The 
line between the illuminated half and the 
half which is not illuminated is the circle of 
illumination. This diagram represents con- 
ditions at the time of an equinox. 



EFFECTS OF INCLINATION OF EARTH'S AXIS 13 



days are longer than the nights, while in the northern hemisphere the 
nights are longer than the days. Twice during the year, therefore, 
on March 21st and September 2 2d, the days and nights are equal 
everywhere. These times 
are known as the equi- 
noxes. The equinox in 
March is the vernal equi- 
nox; that in September 
is the autumnal equinox. 

When the earth is in 
the relation to the sun 
shown in the position 
marked June 21st, Fig. 3, 
the days are longest in 
the northern hemisphere, 
the sun is highest in the 
heavens at noon, and its 
rays fall perpendicularly 
on the surface of the earth 
farther north (23 27'+) 
than at any other time. 
This is the summer solstice 
(Fig. 8). The winter sol- 
stice occurs six months 
later, when the sun 's rays 
strike the earth vertically 
23^"° (nearly) south of 
the equator (Fig. 9), and 
when the days of the 
southern hemisphere are 
longest and those of the 
northern shortest. Figs. 
7, 8, and 9 also show that 
the days and nights are 
always equal at the equa- 
tor, since the equator is 
always bisected by the 
circle of illumination. 
Days and nights are not 
always equal in any other 




Fig. 9. 

Fig. 8. Diagram illustrating the effect of 
inclination of the earth's axis on the length of 
day and night. In the figure, more than half 
of every parallel of the northern hemisphere is 
illuminated. The days in the northern hemi- 
sphere are therefore more than twelve hours 
long, since the half of each parallel is the meas- 
ure of 180 of longitude, and 180 of longitude 
corresponds to twelve hours of time. Similarly 
less than half of every parallel of trie southern 
hemisphere is illuminated, and the days are 
therefore less than twelve hours long. 

Fig. 9. The relation of the earth to the 
sun's rays at a time six months later than that 
represented in Fig. 8. The conditions of day 
and night in the hemispheres are reversed. 



14 



EARTH RELATIONS 




Sp&A 



latitude, unless at the poles, where there is one day (or period) of six 
months of light, and one night (or period) of six months of darkness. 
The relative duration of daylight and darkness, and the angle 
at which the sun 's rays strike the earth, are the chief causes of changes 
of seasons. Thus at the equator, where the hours of day and night 
are always equal, and the sun's rays nearly vertical at all times of 
the year, seasons differ but little, while toward the poles, say in 

Lat. 6o°, where days and 
nights are very unequal 
most of the time, seasons 
differ greatly. 

It will be seen, therefore, 
that most of our methods 
of reckoning years, seasons, 
days, distances and posi- 
tions, weights, and direc- 
tions depend on the various 
earth relations. 

Apparent motion of the 
sun. The effect of the in- 
clination of the axis of the 
earth is to make the sun ap- 
pear to move north and south 
once during each revolution of the earth about the sun. That is, 
the revolution of the earth about the sun, while it rotates on an in- 
clined axis, makes the sun appear to move from a place where its rays 
are vertical 23^° (nearly) north of the equator (direction 5, Fig. 10), 
to a place where they are vertical 23^° (nearly) south of the equator 
(direction W), and back again, in one year. The result, so far as the 
earth is concerned, is as if the sun moved from S, which corresponds 
to the time of the summer solstice, to Sp & A, which corresponds 
to the time of the autumn equinox, then to W, which corresponds to 
the time of the winter solstice, then back again to Sp & A, which 
corresponds to the spring equinox, and finally to S, while the earth 
is making one circuit about the sun. 

When the sun is vertical at points north of the equator, the days 
are longer than the nights in the northern hemisphere, and the sun 's 
rays strike the surface in the northern hemisphere more nearly ver- 
tically than they do in the southern hemisphere. The greater number 
of hours of sunshine and the more nearly vertical rays explain the 



Fig. 10. Diagram illustrating the appar 
ent motion of the sun. 



MAPS AND MAP READING 15 

warmth of our summer, even though the earth is then farthest from 
the sun. In high latitudes, as in western Canada, the long period of 
sunlight (16 to 18 hours) is an important factor in the successful 
cultivation of crops, in spite of the short summer. When the sun is 
vertical at the equator, days and nights are equal everywhere, and 
when the sun is vertical south of the equator, days are longer than 
nights in the southern hemisphere, and the sun's rays are more nearly 
vertical there than in the northern hemisphere. 

The northernmost parallel where the sun's rays are ever vertical 
is called the tropic of Cancer. The corresponding southernmost 
parallel is the tropic of Capricorn. The tropics are nearly 23^"° 
(23 27'+) from the equator, because the axis of the earth is inclined by 
that amount toward the plane of its orbit. The sun is vertical at the 
tropic of Cancer at the time of the summer solstice, and at the tropic 
of Capricorn at the time of the winter solstice. The parallels just 
touched by the circle of illumination at the time of the solstices are 
the. polar circles. They are as far from the poles as the tropics are 
from the equator. They are therefore in latitude about 66>^°. 
The one in north latitude is the Arctic circle, and the one in south 
latitude is the Antarctic circle. 

Within the polar circles the differences of the seasons are chiefly 
a matter of daylight and darkness. Between the tropics there are 
no changes of seasons like those of the United States. Hence it is 
only between the polar circles and the tropics that there are four 
seasons of the year, to be called truly spring, summer, autumn, and 
winter. c^-~ 

Maps and Map Reading 

What is known of the earth 's surface may be represented in vari- 
ous ways — by globes, models, and maps. Globes have the great 
advantage of showing without distortion the distribution of land and 
sea, and other large surface features. It is not practicable, however, 
to make them large enough to show minor features, and, even apart 
from this, they are not suited to all purposes. Models, or relief maps, 
reproduce on a small scale the unevenness of the earth 's surface. In 
order that the elevations may stand out clearly, their height is exag- 
gerated greatly on most models, which are likely, therefore, to give 
false impressions. 

Map projections. The necessity of representing part or all of the 
earth on a flat surface led very early to the making of crude maps. 



i6 



EARTH RELATIONS 




Fig. ii. Map representing relief by 
hachures. (U. S. Geol. Surv.) 



It is, of course, impossible to show the rounded surface of the earth 
on a flat surface without exaggerating or reducing certain parts, 
so that each of the many methods {projections) devised from time 

to time for representing the 
meridians and parallels of a 
globe on a plane surface, 
involves more or less distor- 
tion. 

Almost all sailing charts and 
many maps of the entire world 
are made on Mercator's projec- 
tion (Fig. 39), named for the 
inventor. A map on Merca- 
tor's projection is accurate at 
the equator, but exaggerates 
areas more and more as the 
poles are approached. Thus 
Greenland (Fig. 39) appears to 
be about half as large as North 
America on a Mercator's map, 
while in reality it is less than one-fifteenth as large. 

Representation of relief on maps. The surface of the land 
is uneven, and it is a matter of importance, in many cases, to show the 
unevennesses {relief) on maps. This is done in various ways. One 
method is by shading — different colors or shades representing 
different elevations (see maps at end of book). Another method is 
by hachures (Fig. 11) — lines drawn in the direction in which the 
land slopes. Where slopes are steep, the lines are made short and 
heavy; where gentle, longer and lighter. Such maps give only a 
general idea of the form of the land. 

Much more exact information may be had from contour-line 
maps. In order to read contour-line maps, it is necessary to know 
that contours are lines drawn on maps to express relief, and that any 
given line runs through points of the same elevation above sea-level. 
This will be understood readily by reference to Figs. 12 and 13. 
Fig. 12 shows a model of an ideal landscape viewed from above, on 
which lines have been drawn connecting places of equal elevation. 
In Fig. 13 the above lines are shown alone; this is a contour map 
of the region represented by the model. By comparison of the model 
and map it will be seen that where the slopes of the former are steep 



WAYS OF REPRESENTING RELIEF ON MAPS 



i7 



the lines of the latter are close together, and vice versa. The vertical 
distance between two adjacent contour lines is the contour interval. 
The contour interval varies on different maps. In regions of low 




Fig. 12. Model of ideal landscape. (U. S. Geol. Surv.) 




Fig. 13. Contour map of the area shown in Fig. 12. (U. S. Geol. Surv.) 



relief an interval of 10 or 20 feet generally is used; in mountainous 
areas an interval of 500 or more feet has to be used in some cases in 
order to avoid having the lines too close together to be read. In 
the map of Fig. 13, the interval is 20 feet, the exact value of the 10c 



1 8 EARTH RELATIONS 

and 200 foot lines being indicated. By counting the lines it will 
be seen that the top of the hill to the left of the river is more than 
260 feet above the level of the ocean in the foreground. It cannot be 
280 feet high, however, for no 280 foot line is drawn. A comparison 
of the model and map will show also how valley depressions are repre- 
sented by contours. 

Terrestrial Magnetism 

The earth is a great magnet, and, like the small magnets with which we are 
familiar, has two poles. One of these poles is called the North Magnetic Pole and the 
other the South Magnetic Pole. One end of the compass needle points toward one 
of these poles, and the other toward the other. If we were to follow the directions 
pointed by the compass needle, we would be led to the North Magnetic Pole in the 
one case, and to the South Magnetic Pole in the other. 

The magnetic poles are far from the geographic poles, the true north and south 
points, and they are not exactly opposite each other. Their positions appear to 
shift a little from year to year, but the change is not known to be great. The 
North Magnetic Pole is in latitude about 70 N., and in longitude 97 or 98 W., 
while the South Magnetic Pole is in latitude 72 25' S., and longitude 155 16' E. 

Questions 

1 . The horizon of a given observer increases as he rises. What does this prove 
concerning the shape of the earth's surface at that place? What further inference 
could be made from the fact that as he ascends his horizon remains circular? 

2. At places east of a given point the sun rises and sets before it does at that 
point. At places toward the west it rises and sets after it does at the station in 
question. What does this indicate as to the surface of the earth? 

3. Why do the sun's rays never fall vertically in latitudes higher than 23^°? 

4. Certain crops are said to mature faster in western Canada than farther 
south in the United States. Suggest a logical reason for this. 

5. How would the seasons at Chicago (42 N.) be changed if the axis of the 
earth were inclined 45 , rotation remaining as now? 

6. Two cities about 690 miles apart, on the same meridian, are located in 
latitude 42 N. and 32 N., respectively. From these facts determine approximately 
the circumference of the earth. 

7. What is the difference in longitude of two places having a difference in 
time of six and one-half hours? 

8. -What is the difference in local time between New York City (74 W.) and 
Chicago (87 36' W.)? 

9. The altitude of the sun at a given place at noon at the time of equinox 
is 50°. What is the latitude of the place? 

10. In what latitudes is the altitude of the sun 20 at noon at the time of equinox? 
n. In what latitudes has the sun a noon altitude of 30 at the time of the 

summer solstice? 

12. What is the altitude of the sun at the equator at noon at the time of the 
summer solstice? 



CHAPTER III 
RELIEF FEATURES OF THE EARTH 

The surface of the land is uneven. The lowest lands are below 
sea-level, and the highest point (Mt. Everest, in the Himalaya Moun- 
tains) is more than five and one-half miles above sea-level. The 
relief of the land surface is therefore not far from six miles. Com- 
pared with the diameter of the earth, even the loftiest mountains are 
slight elevations, for the height of Mt. Everest above the sea is equal 
to only V1436 part of the polar diameter of the earth. On a globe 
10 feet in diameter this would correspond to one- twelfth of an inch. 

The sea bottom also is uneven, and its relief is a little greater than 
that of the land. Since the highest points of land are nearly six miles 
above the sea, and the lowest parts of the sea bottom about six miles 
below, the relief of the surface of the solid part of the earth (lithosphere) 
is almost twelve miles. If its surface were even, the water of the ocean 
would cover the whole earth to the depth of about 9,000 feet. 

Relief Features of the First Order 

Continents and ocean basins. The average elevation of the 
lands above sea-level is a little less than half a mile, while the average 
depth of the oceans is about two and one-half miles. Were the height 
of lands in middle and high latitudes equal to the average depth of the 

Mountains. 
gateau ^~v s\ — d/^„„„ 



Fig. 14. Diagram to show the distinction between an elevated continental 
area and an ocean basin. The steep slope (much exaggerated) at the left of the 
ocean basin is the line of contact between the two, and is the real border of the 
continental area. The ocean covers the lower part of the continental tract, 
namely, the continental shelf. The diagram also shows the general relation 
between low mountains, such as the Appalachians, a low plateau, and a coastal 
plain. The continental shelf is a continuation of the coastal plain. 

19 



2o RELIEF FEATURES OF THE EARTH 

oceans, much of each continent would be too high and cold to support 
a dense population. The continents and the ocean basins are relief 
features of the first order. 

The oceans have an area (143,000,000 square miles) more than two 
and one-half times as great as that of the lands (54,000,000 square 
miles). About most continental borders, the water is shallow (less than 
600 feet) for some miles. The bottom beneath this shallow water is the 
continental shelf (Fig. 14). At their sea-ward edges, the continental 
shelves descend, by rather steep slopes, to the ocean basins. Por- 
tions of the continental shelves have been built up from deeper water 
by the deposition of sediments washed down from the land; other 
parts are due to the sinking of former land areas; and still others are 
the result of the wearing back of the land by waves. 

Many islands stand on the continental shelves, and represent higher areas 
whose lower surroundings have sunk, or been cut by waves, below sea-level. In 
many cases a slight elevation of the continental shelf, or a slight lowering of the 
sea, would join these islands to the mainland. Thus a rise of 300 feet would trans- 
form most of the area of the Baltic and North seas into land, and unite Great 
Britain with the continent. Such a change would modify greatly conditions in 
Great Britain. Separation from the continent has freed the United Kingdom from 
the need of a large standing army, and favored the development of extensive sea 
interests, which required the maintenance of a large navy to protect them. 

Most islands of the ocean outside the continental shelves are 
volcanic cones, or coral islands associated with them. Their combined 
area is only about three-fourths that of the state of Illinois. 



Fig. 15. Land and water hemispheres. 

Grouping of the continents. The northern hemisphere con- 
tains more than twice as much land as the southern. If the earth be 



PLAINS, PLATEAUS, AND MOUNTAINS 21 

divided into two hemispheres, one with its center in England and 
the other in New Zealand (Fig. 15), the first would contain about 
six-sevenths of all the land, and might be called the land hemi- 
sphere, while the other would contain only about one-seventh of 
the land, and might be called the water hemisphere. Even in the 
land hemisphere, however, the water would cover rather more 
than half the surface, while in the water hemisphere it would cover 
about fourteen-fifteenths of it. Since the northern hemisphere 
contains two-thirds of the land, and a still larger proportion of 
the productive land, it has always supported a vast majority of the 
human race. 



Relief Features of the Second Order 

The more strongly marked features of the continents and of the 
ocean basins are relief features of the second order. The continental 
areas are made up of plains, plateaus, and mountains. Some of their 
relations are shown in Fig. 14. 

Plains. Plains are the lowlands of the earth. They may be but a 
few feet above the sea, or they may be hundreds or thousands of feet 
above it; but if so high as a thousand feet, they are in most cases far 
from the sea, and distinctly lower than some of the other lands about 
them. Plains differ widely among themselves, not only in height, 
but in position, size, shape of surface, fertility, origin, and in various 
other ways. Different names are given to various sorts of plains, the 
names being intended to call attention to some one feature. Coastal 
plains border the sea, and interior plains axe far from it, or are separat- 
ed from it by high lands. The plains of the Atlantic and Gulf coasts 
illustrate the first class, while a large part of the area between the 
Appalachian Mountains and the Rocky Mountains is a great interior 
plain (Plate 1). 

Plateaus. Plateaus are highlands with considerable summit areas; 
but no great elevation is necessary to make a flattish area of land a 
plateau. In general, a plateau is so situated as to appear high from 
at least one side. Thus if a coastal plain rises gradually from the sea 
to a height of 200 feet, and then rises by a steeper slope to another 
broad tract of land which stands 200 feet higher (Fig. 14), the upper 
tract would be called a plateau. The Piedmont Plateau, which lies 
between the Appalachian Mountains and the Atlantic Coastal 
Plain, is not very high, but it is enough higher than the Coastal 



22 RELIEF FEATURES OF THE EARTH 

Plain to be distinctly set off from it. A large part of this plateau 
is, however, not so high as much of the great interior plain of the 
continent. 

Some plateaus lie between mountains on the one hand and plains 
on the other, as in the case of the Piedmont Plateau. Others lie be- 
tween mountains, as the plateaus of central Asia (Fig. 16), Mexico, 

Caucasus Mts. Himalaya Mts. Nan-Shan Mts. 



Fig. 1 6. Section across Asia, showing plateau between the Himalayas and the 
Nan-Shan Mountains. 

Sierra Ui "f a Ro ^ 

Mts r*- Mu - 

/V~— ^_, />^- ^C\^ ^__ Mississippi Basin s^~— — _^__ 

Fig. 17. Section across North America, showing plateaus between the moun- 
tains in the western part. 

and western United States (Fig. 17). Other plateaus rise directly 
from the sea, as Greenland and parts of Africa. The total area of 
plateaus is great, though less than that of plains. 

Mountains. Mountains are conspicuously high lands with slight 
summit areas (Fig. 18). The tops of the loftiest mountains are be- 
tween five and six miles above the sea, but most mountains are not 
half so high. The highest mountains tower above any plateaus, 
but many mountains are lower than the highest plateaus. Few 
mountains reach the height of the Plateau of Tibet, 15,000 to 16,000 
feet. 

Mountains are unlike plateaus of similar elevation in having little 
area at the top. In the case of mountain peaks, this is shown by 
the name. A mountain ridge may be long, but in most cases its top 
is narrow. Numerous peaks or ranges near together make a moun- 
tain group or chain; but even in great mountain groups there is no 
large expanse of land at the summit level. 

Where mountains rise abruptly to great heights above their surroundings, they 
are the most impressive and awe-inspiring features of the earth. In not a few 
cases they rise from low, warm plains to such heights that their summits always 
are covered with snow. Nowhere else are such extremes of climate found so close 
together. 






MINOR TOPOGRAPHIC FEATURES 23 

Mountains are the third of the three topographic types of the 
second order, as they appear on the lands of the earth. In this group- 
ing of mountains, only great groups or systems of mountains, such as 
the Appalachians, the Rockies, the Alps, the Himalayas, and the 
Andes, are considered. 

Most mountain ranges are situated near the edges, rather than in 
the interiors, of the land masses, and most of the loftier mountain 
chains are not far from the shores of the greatest ocean. The conti- 




Fig. 18. Mountains rising conspicuously above a plain. Southern California. 

nental slopes to the Pacific Ocean are therefore shorter and steeper 
than those to the Atlantic and Arctic oceans. About one-third of 
the land drains to the Atlantic Ocean, one-sixth to the Arctic, one- 
seventh to the Pacific, and one-eighth to the Indian. The drainage 
of the rest of the land (22%) fails to reach the sea, and is lost in 
dry interior basins. 

Subordinate Topographic Features 

The surfaces of most plains and plateaus are uneven, while the 
very name of mountain suggests ruggedness. Irregularities of surface 
consist of elevations, such as ridges and hills, above the general level, 
and of depressions, such as valleys and basins (depressions without 
outlets) , below it. The elevations and the depressions are bordered by 
slopes, which, when very steep, are called cliffs. Ridges, hills, valleys, 
basins, flats, and cliffs affect mountains, plateaus, and plains; but in 
most cases they are more pronounced in mountains and plateaus than 



24 RELIEF FEATURES OF THE EARTH 

on plains. These minor unevennesses of surface are topographic 
features of the third order. The key to their history is found in changes 
now taking place on the land (Chapter XV) , or in those which have 
taken place in recent times. 



Comparison of the Continents 

The position, form, size, and general relief of the continents are 
of fundamental importance, since these things determine, in large 
measure, their fitness for human occupation. Europe (Plate IV), 
the smallest continent except Australia, lies almost entirely in the 
north temperate zone. It widens rapidly toward the south, so that 
its east and west extent along the line of the Mediterranean, Black, 
and Caspian seas is nearly three times that along the Arctic Ocean. 
No other continent has an outline so irregular. Great arms of the 
sea extend far inland, modifying climate and helping commerce by 
bringing most parts of the continent into close contact with the sea. 
More than half of Europe is less than 600 feet above sea-level, and 
only one-sixth is over 1,500 feet. Many rivers serve as natural high- 
ways into the interior. Some of those in the west are unfrozen 
throughout the year. Europe has no tropical section, and no dry 
desert. 

Asia (Plate V), the largest of the continents, is nearly 4^ times the 
size of Europe, and nearly 5^ times as large as the United States. 
It extends somewhat farther north than Europe, and much nearer 
the equator. Less than one-fourth of Asia is below 600 feet above the 
sea, and about one-sixth is above 6,000 feet. The average elevation 
is nearly three times that of Europe. A central region of high pla- 
teaus and mountains receives little rain, and is of slight value to man. 
The longest drainage slopes are toward the Arctic. Because of these 
things, one-half of Asia is relatively inaccessible. Asia has only 
about one-third as long a coast-line as Europe in proportion to its 
area. Its great size and relatively compact form make it the conti- 
nent of climatic extremes. From a physical standpoint Europe and 
Asia form one continent (called Eurasia), but for historical and other 
reasons they usually are separated. 

Australia (Plate VII) is only a little larger than the United 
States, and is divided almost in halves by the tropic of Capricorn. 
The coast, though less regular than that of Africa and South America, 
has few harbors compared to Europe and North America. Because 



THE CONTINENTS COMPARED 25 

of its position, size, compactness, and topography, much of Australia 
is arid (p. 106). Australia is the most isolated of the continents. 

About two-thirds of Africa (Plate VI) are within the tropics. 
Broadly speaking, the continent consists of a great plateau, bordered 
in places by a narrow coastal plain. At the south, the plateau is 
3,000 to 5,000 feet above sea-level; at the north, 1,000 to 2,000 feet. 
Only one-eighth of the land (less than in any other continent) is below 
an elevation of 600 feet. The rivers descend in rapids or falls to the 
coastal lowlands. More than one-third of the continent is desert, 
while other large areas are semi-arid. Africa has the most regular 
coast of any continent. Europe, with the most irregular outline, 
has more than six times as much shore-line as Africa, in proportion 
to its area. Although one of the most ancient civilizations had its 
seat in Egypt, Africa has remained to our own day the "dark conti- 
nent." The conditions indicated above have helped greatly to 
bring this about. The fact that much of the coast is without 
harbors, and that navigation of even the larger rivers is interrupted 
near their mouths by falls and rapids, delayed exploration, conquest, 
and commerce. Both the vast deserts and the dense equatorial forests 
retarded native progress, and discouraged European settlement. 

Like Africa, South America (Plate III) is largely within the tropics 
and is very compact, with few great indentations, peninsulas, or is- 
lands. On the other hand, the proportion of desert is much less, and 
of lowlands much greater. Two-fifths of South America are below 
600 feet, and two-thirds under 1,500 feet. 

In North America (Plate I), as in Europe, most of the land is in 
middle latitudes. Unlike Europe, North America presents its greatest 
width to the cold polar seas. North America ranks next to Europe 
and South America in the relative extent of its lowlands. Nearly 
one-third of the continent is below 600 feet, and nearly two-thirds 
below 1,500 feet. The vast interior plain stretching from the Arctic 
Ocean to the Gulf of Mexico has an unequaled system of navigable 
waterways. Except Europe, North America has the longest shore- 
line in proportion to its size. The greatest indentation, the Gulf of 
Mexico, affects the climate of eastern United States profoundly 
(p. 85). Except in the far north, most of the indentations have 
commercial importance. 



26 RELIEF FEATURES OF THE EARTH 



Questions 

i. South America and Africa have few islands about their borders. What 
does this suggest concerning the width of their continental shelves? Does it 
prove anything about the width? 

2. Soundings along the eastern coast of the United States have shown that 
depressions like river valleys extend across the continental shelf from the mouths 
of various rivers. What do such depressions suggest concerning the history of those 
parts of the continental shelf where they occur? 

3. From the comparison of the continents given on pages 24-25, which ones 
appear best fitted to contain the most advanced nations? Which ones seem 
least fitted to do so? 

4. Most people live on plains. Would it therefore be better, from the human 
standpoint, if the earth were without mountains? Reasons? 



CHAPTER IV 
THE NATURE AND FUNCTIONS OF THE ATMOSPHERE 

General Conceptions 

Relation tp rest of earth. Air is essential to the life of the earth, 
and to most processes in operation on the earth 's surface. It helps 
to distribute moisture, it makes the extremes of heat and cold less than 
they would be if it did not exist; and it is a leading factor in the 
formation of soil. Furthermore, the atmosphere is not merely an 
envelope of the rest of the earth, for it goes down into the soil and 
rocks as far as there are holes and cracks, and its constituents are 
dissolved in the waters of sea and land. 

Weight of air. When the atmosphere is still, we are hardly 
conscious of its existence, but many familiar phenomena show that 
air is very substantial. Thus wind, which is only air in motion, may 
be so strong that trees and buildings are blown down by it. A wind 
blowing 30 miles an hour exerts a force of nearly 60,000 pounds on 
the side of a house 60 feet long and 20 feet to the eaves. The pressure 
of still air, that is, its weight, is nearly 15 (14.7) pounds on every 
square inch of surface at sea-level. In other words, its weight is 
equal to that of a layer of water completely covering the earth to a 
depth of 33 feet. 

Density. The atmosphere is made up of gases. The particles 
of which the air is composed are nearer together at low altitudes than 
at high altitudes. At its bottom, the air is pressed down by all the 
air above; at the height of 1,000 feet the air is pressed down by all 
above that level, and so on. Hence the lowest air is under most 
pressure and is densest. One-half the atmosphere (by weight) lies 
below a plane about 3.6 miles above sea-level, and three-fourths of it 
below a plane 6.8 miles above the same level. Nearly three-fourths 
of the atmosphere lies below the top of the highest mountain. It 
is partly because the air is less dense at high levels that mountain- 
climbing is difficult. The body is not accustomed to the lessened 
pressure, and it causes discomfort. 

27 



28 NATURE AND FUNCTIONS OF THE ATMOSPHERE 



Height. The actual height of the atmosphere is not known, 
though something is known about it (Fig. 19). 

(1) The greatest altitude reached by any mountain-climber is 
about 24,000 feet. This shows that the air extends to a height of 
more than four and one-half miles. 

(2) Men have gone up more than six miles in balloons. In some 
cases, the men in the balloons became unconscious before this height 
was reached, and in other cases, where oxygen was carried for breath- 
ing, the chief discomfort was from cold. Balloons without men have 

risen eighteen miles. At this 



tf ,gh Clouds (Wmiles) 



Highest Mou mtain (6 m,le s ) 
■ Hi|hes^_Mo_u_ntain_Ascent_ (4% ^jjj- - -, 

low Cjouds ('/smi/e ) 




Fig. 19. Diagram to show relative 
altitudes in the atmosphere. 



height the air is still dense 
enough to carry the balloon. 
This shows that the air extends 
up more than eighteen miles. 

(3) On almost any clear 
night "shooting stars" may be 
seen. Shooting stars, or me- 
teors, are small, solid bodies 
which come into the earth's 
atmosphere from space outside. 
They are very cold when they 
enter the atmosphere, for the temperature of space is very low 
(probably about — 45q°F.). In passing through the atmosphere, 
meteors are heated by friction with the air, and when they get red-hot, 
they may be seen. The height at which they begin to glow has been 
calculated in some cases, and found to be, at a maximum, nearly 200 
miles above sea-level. This shows that the atmosphere is much more 
than 200 miles high, for the meteors must have come through the rare, 
cold, upper air a long distance before becoming red-hot by friction with it. 
From these considerations it appears to be certain that the air 
extends more than 200 miles above the rest of the earth, but how 
much more is unknown. Except for a few miles near its bottom, it 
is, of course, very thin (rare). 



Composition 

Principal constituents. The composition of the atmosphere is 
nearly the same at all times and at all places where it has been ana- 
lyzed. In its lower parts, at least, it is made up chiefly of two gases 
— (1) nitrogen, which makes up about 78 per cent of dry air, and (2) 



IMPURITIES IN THE AIR 29 

oxygen, which makes nearly 21 per cent. Some scientists think its 
composition at great heights may be very different from that below. 

Besides these two gases, there are several lesser constituents, two 
of which, carbon dioxide and water vapor, are very important. The 
former makes up about 3 /ioooo by weight of the whole atmosphere, 
and its amount is nearly constant from day to day, and from year to 
year. Water vapor is water in particles too small to be seen. The 
total amount in the atmosphere is not known to vary much, but the 
amount varies greatly from place to place, and it varies much from 
time to time in the same place. Even in the driest deserts the air is 
never without water vapor. Several other gases exist in the air, but 
among them ozone only is known to be of much importance. 

The gases of the air are mixed with one another, and each of them 
retains its own qualities in the mixture. Oxygen behaves much as if 
no nitrogen were present, and the nitrogen as if there were no oxygen. 

Impurities. The air always contains some gases which are 
impurities, though they are not necessarily harmful to life. Some 
such gases arise from the burning and decay of organic matter, 
others from chemical processes used in manufacturing, and still others 
from volcanic and other vents in the earth's crust. Although the 
total amount of gas which enters the air in these ways is small in 
comparison with the volume of the atmosphere, it would seem very 
great if stated in terms of weight or volume. For example, it is 
estimated that at least 1,000,000,000 cubic feet of natural gas escape 
unused into the air each day in the United States. Quantities of gas 
are poured into the air, too, from chimneys. The air always contains, 
as impurities, numerous solid particles, such as dust, and germs or 
other organic matter. These vary in amount and character from 
place to place, and from time to time. 



Relations of the Different Constituents to Life 

Nitrogen. Nitrogen is inactive. Though it enters the lungs 
with oxygen in breathing, it does not appear to be of direct use to 
animals. Indeed, its chief function in relation to life is often said 
to be "to dilute the oxygen." It is important to note, however, 
that indirectly nitrogen is of great importance to both plant and 
animal life. Most plants use the small quantities of nitrogen com- 
pounds in the soil. Nearly all crops, if grown year after year in the 
same place, take out so much of the nitrogenous matter as to decrease 



3 o NATURE AND FUNCTIONS OF THE ATMOSPHERE 

the fertility of the soil. A few plants, such as clover, alfalfa, peas, 
and beans, add nitrogen to the soil. Certain bacteria associated 
with these plants take nitrogen from the air and combine it with other 
elements, and the plants then store it in their roots, stalks, etc. It 
is therefore important to grow nitrogen-fixing plants in rotation with 
other crops, and turn them under the soil. 

Oxygen. Oxygen from the air is consumed all the time by ani- 
mals. Air-breathing animals take it from the air directly, and water- 
breathing animals take it from the water in which it is dissolved. 
Oxygen is used by plants also, especially by green plants, and it is 
used wherever combustion (burning) or decay is going on, for com- 
bustion is primarily the union of oxygen with carbon, and decay 
is very slow combustion. The heat developed by combustion (as 
of coal) warms houses, and produces steam to run trains, drive 
machinery, and serve man in many other ways. Oxygen from 
the air combines with various constituents of rocks to form new com- 
pounds, and in so doing helps to form soil (p. 162). 

In spite of the fact that oxygen is being consumed all the time, 
its amount does not appear to grow less from year to year. It must, 
therefore, be supplied to the air about as fast as it is used up. Plants 
break up the carbon dioxide of the air into carbon and oxygen, and 
set some of the oxygen free. This is the greatest source of supply. 
Small amounts of oxygen also reach the atmosphere from volcanic 
vents, and in other ways. It will be seen that plants, through their 
relation to oxygen and nitrogen, play an important part in supplying 
animals with both these elements. 

Carbon dioxide. The carbon dioxide of the air, though a small 
constituent, is extremely important. It is being made constantly 
by the burning of all kinds of fuel and by the decay of all organic 
matter. It is also added to the air by the breathing of animals. 
Every 1,000,000 human beings breathe out about 2.5 tons per hour. 
It also comes out of many volcanic vents in great quantities. 

From these various sources, carbon dioxide is supplied to the atmosphere 
rapidly. About three-fourths of common soft coal is carbon. The carbon of a ton 
of such coal, united' with oxygen from the air (3ms. of carbon unite with 8lbs. of 
oxygen), would make more than 2^ tons of carbon dioxide, all of which goes into 
the atmosphere. A ton of hard coal, which contains more carbon, would produce 
still more carbon dioxide. Nearly a billion tons of coal are mined each year, and 
most of this is burned. When all sources of carbon dioxide are considered, it seems 
safe to say that carbon dioxide is being supplied to the atmosphere at the rate of 
about 75 tons per second. 



CARBON DIOXIDE AND LIFE 31 

Because of its close relations to combustion, respiration, and 
decay, the amount of carbon dioxide in the air of cities is greater than 
in the open country. The amount in the air of London occasionally 
becomes five times the normal quantity, while in badly ventilated 
schoolrooms, theaters, and workshops, it is sometimes ten times the 
normal amount. The conditions which increase the amounts of 
carbon dioxide in city air usually increase the amounts of various 
other harmful gases. Such conditions are injurious to health. The 
widespread movement to "purify city air," largely by doing away 
with smoke, is an attempt to remedy these conditions. 

In spite of constant additions, the amount of carbon dioxide in 
the air does not increase permanently enough to be noted. This gas, 
therefore, must be taken out of the atmosphere about as rapidly as 
it comes in. It is taken from the air chiefly (1) by green plants, of 
which it is the main food, and (2) by uniting with mineral matter 
in the solid part of the earth. It supports not only most plants, but 
indirectly most animals, for the latter feed on vegetation, or on 
other animals that live on plants. By uniting with mineral matter 
it helps to form soil. 

The carbon dioxide of the air has still other important functions. 
The earth is radiating heat into space all the time, somewhat as a hot 
stove radiates heat into its surroundings, and carbon dioxide has the 
power of holding much of this heat. It therefore serves as a blanket 
to hold in the heat of the earth, and, thin as the blanket is, it is more 
effective, in this respect, than the denser blanket of oxygen and 
nitrogen. If it were thicker, the temperature would be still higher. 
It is thought possible that at certain times in the distant past, as 
when magnolias grew in Greenland, the amount of carbon dioxide in 
the air may have been greater than now; and that at other times, 
when the climate was cold in low latitudes, the amount may have been 
much less than now. 

Water vapor. The water vapor in the atmosphere is a variable 
quantity. It is all the time entering the atmosphere by evaporation, 
and it is all the time being condensed and precipitated from the 
atmosphere as rain, snow, etc., to be again evaporated, condensed, 
and precipitated. The larger part of both water vapor and carbon 
dioxide is in the lower part of the atmosphere. Like much of the 
carbon dioxide, the water vapor is making continuous rounds. Its 
precipitation supplies the water for wells, the flow of springs, the 
maintenance of lakes, streams, and glaciers, and for the life of plants 



32 NATURE AND FUNCTIONS OF THE ATMOSPHERE 

and animals. The bodies of animals, including human beings, are 
about four-fifths water. The tissues of annual plants are three- 
fourths water; of perennials, nearly half. To produce a bushel of 
corn, from 10 to 20 tons of water are required. 

The amount of water vapor which the atmosphere is capable of 
containing at any time depends on temperature; but other things, 
such as the available supply, help to determine the amount which 
there is in the air in any one place. Like the carbon dioxide, the 
water vapor of the air helps to keep the earth warm. 

Dust. All solid particles held in the air are dust. They are 
not ordinarily seen except on dry, windy days, but dust from the air 
is constantly settling everywhere, indoors and out, whenever the 
air is dry. Dust may be seen readily indoors if a room is darkened 
and light allowed to enter through a narrow crack or small hole. 
Even air which appears clear may in this way be seen to contain 
countless particles of solid matter. The amount of dust is sometimes 
very great, as over cities and in dry and windy regions. During the 
fogs of February, 1891, it was estimated that the amount of dust, 
deposited on roofs in and near London was six tons per square mile. 
Dust-polluted air is believed to favor diseases of the lungs, like 
tuberculosis. 

Some years ago a method was devised for counting the dust particles in a 
given volume of air. The result showed that in the air of great cities there are 
hundreds of thousands of dust particles in each cubic centimeter of air (a cubic 
centimeter is less than J /i6 of a cubic inch); and. that even in the pure air of the 
country, far from towns and factories, there are hundreds of motes per cubic centi- 
meter. 

Like carbon dioxide and water vapor, most of the dust is found be- 
low an altitude of 10,000 feet. Its relative absence at high altitudes 
increases the intensity of the sunshine there by day, and helps to 
bring about low temperatures at night. 

Dust particles in the atmosphere are important in several other 
ways. They scatter the light of the sun in such a way as to illuminate 
the whole atmosphere. Without dust in the air, all shady places would 
be in darkness. The sun would appear, probably in dazzling brilliance, 
shining from a black sky in which the stars would be visible even in 
the daytime. The blue color of the sky and the sunset and sunrise 
tints are influenced by the dust in the atmosphere. Dust particles 
also serve as centers about which water vapor condenses. 



QUESTIONS 33 



Questions 

i. State the conditions (all of them) which would tend to make the country 
air dusty at a given point in northern United States. 

2. What conditions favor an increase in the amount of dust in the air of cities 
in summer? In winter? 

3. Compare and contrast the purity of the air (1) over oceans and over 
lands; (2) in dry and in moist regions; and (3) at high and at low altitudes. 

4. Would you expect the average amount of carbon dioxide to be greater in 
the air of cities or of the open country? Why? What processes tend to equalize 
the amount over country and cities? 

5. Give at least three reasons why the amount of carbon dioxide in the air 
(especially of great cities) tends to vary in amount between summer and winter. 

6. Why do people accustomed to low altitudes breathe very much faster in 
high altitudes? 

7. Indicate various ways in which the extreme elasticity of the air favors 
human activities. 



CHAPTER V 
CLIMATIC FACTORS: TEMPERATURE 

General Considerations 

Besides the composition of the atmosphere, various other things 
connected with it are of great importance to life. The things which 
make up climate (climatic factors) are especially important. The 
chief climatic factors are (i) temperature, (2) moisture, and (3) air 
movements, or wind. 

Importance of heat. Were it not for the effect of the atmosphere 
on temperature, life could not endure the heat of day or the cold of 
night, and the earth would be a desolate, lifeless waste. The tem- 
perature which most concerns land life is the temperature of the air 
in which it lives. The air is warmed chiefly by the sun. The heat- 
ing power of the sun is proved by the fact that days are warmer than 
nights, and that sunny days are warmer than cloudy ones. The 
rare exceptions to these general facts need not be considered now. 

Measurement of heat. Variations of temperature from time to time and 
from place to place are so important that it is necessary to have some easy way of 
measuring and recording them. Temperature is measured by the thermometer, 
which consists of a glass tube of uniform diameter, except for a bulb at the lower 
end. The bulb and the lower part of the tube are filled with some liquid, generally 
mercury, and this is heated until it boils. The boiling mercury fills the tube and 
expels all air, and while it is boiling the tube is sealed, the heat being withdrawn at 
the same moment. On cooling, the mercury contracts and fills the lower part of 
the tube only. Whenever the temperature rises, the mercury expands and rises 
in the tube, and when the temperature falls, the mercury contracts and sinks. The 
amount of rise or fall of the mercury shows the amount of change of temperature. 

A scale is marked on the tube so that the temperature may be read from it. 
Two scales are in common use — the Fahrenheit (F.) and the Centigrade (C). On 
the Fahrenheit scale the temperature of boiling water (at sea-level under normal 
pressure) is marked 21 2 ; on the Centigrade scale, ioo° (Fig. 20). The tempera- 
ture of melting ice (freezing point) is marked 32 on the former scale, and o° (zero) 
on the latter. Between the freezing and the boiling point on the Fahrenheit scale 
there are 180 degrees, and on the Centigrade scale 100 degrees. It follows that 
i° C. js equal to i4/ s ° F. Zero on the Fahrenheit scale is 32 below the freezing 
point, and 20 below zero Fahrenheit (written — 20 F.) means 52 (32°+ 20 ) 

34 



HEAT FROM THE SUN 



35 



below the freezing point. The Centigrade scale is simpler than the Fahrenheit, 
and is used generally in scientific work and in most European countries. 

We often have occasion to use the temperature of a given place at a given time, 
as that of New York at noon on July 4th; but we also have occasion to use the 
records of temperature in other ways. From a sufficient number of temperature 
records, spread properly over a year, an average temperature for that year may be 
obtained. Similarly, averages for shorter periods, as seasons, months, and days, 
are possible, called average seasonal, monthly, and daily 
temperatures. The average temperature of one year for a 
given place is, as a rule, somewhat different from that of 
the preceding or following year. The average temperature 
for a goodly number of years gives its mean annual tem- 
perature. Similarly, it is necessary to take the averages 
for many Januarys to get the mean monthly temperature 
for that month. The highest temperature during any 
period is its maximum temperature and the lowest, its 
minimum temperature. 

Sun heating : insolation. The northern and 
southern hemispheres receive the same amount 
of heat from the sun each year, but, because of 
the inclination of the earth's axis, they do not 
receive the same amounts at the same seasons. 
Both receive the same amounts of heat per day 
only at the times of equinox. The amount of 
heat received by the surface of land and water is 
far less than the amount coming to the top of 
the atmosphere, for much is absorbed in passing 
throug the air. 

(1) Other things being equal, any part of 
the earth should get most heat per day when 
the sun shines there the greatest number of hours. During a part 
of the summer of the northern hemisphere, latitudes above 66j4° 
have sunshine continuously (except for clouds) for more than 24 
hours. So far as hours of sunshine are concerned, therefore, 
these latitudes should then receive more heat per day than other 
parts of the earth. If there were no atmosphere, the surface of 
the earth at the North Pole would receive, on the 21st of June, 
about one-third more heat during 24 hours than the surface of an 
equal area at the equator. But the amount of heat which reaches 
the bottom, of the air'aX. the pole on the 21st of June is much 
less than that received at the bottom of the atmosphere at the 
equator. 



Fig. 20. Diagram 
to represent Fahren- 
heit and Centigrade 
scales. 



36 



CLIMATIC FACTORS: TEMPERATURE 







\ 




/ . 


Equator 


-^2 N 




\ V 




\ V 




\ \ 




Y \ 




\ 


\ 










— 








' 




I 




~L 


/ 




/■ 




/ / 




^ 


X 


-^2 y 



(2) Other things being equal, the surface of the land or water gets 
most heat where the sun 's rays are most nearly vertical, because (a) 
the rays are there most concentrated, and (b) they pass through 
a less thickness of the air. This is shown by Fig. 21. A given 
bundle of rays, 1, falling vertically on the surface, is distributed 

over a given area, while an 
equal bundle of rays, 2, falling 
obliquely on the surface, is 
spread over a greater area, and 
therefore heats each part less. 
The rays oblique to the sur- 
face, 2, have passed through a 
greater thickness of air, and 
more of their heat has been ab- 
sorbed by it before they reach 
the surface of the land or water. 
These facts help to explain why 
the surface at the poles does not 
get warmer than an equal area 
at the equator, even with 
months of continuous sunshine 
at the former places, and but 
12 hours at a time at the latter. 
The snow and ice of polar regions prevent them from getting warm, 
even during the months when much heat is received (p. 37). 

The angle at which the sun 's rays reach the earth varies from place 
to place, and from time to time at the same place, because of the 
inclination of the earth's axis. This is illustrated by Figs. 8 and 9, 
which have been explained. 

Distribution of insolation. From Fig. 10, which has been 
studied, we see that when the sun's rays come to the earth from the 
direction W (perpendicular 23^° south of the equator), they are 
more oblique than at any other time in the northern hemisphere, and 
less oblique than at any other time in the southern hemisphere. At 
the same time the days are longer in the southern hemisphere than in 
the northern. Hence there are two reasons why the southern hemi- 
sphere receives more heat than the northern at this season, namely (1) 
more nearly vertical rays, and (2) more hours of sunshine. 

After the time (winter solstice, December 2 2d) when the sun's 
rays are vertical at 23^° S., they become perpendicular to the sur- 



Fig. 21. Diagram to illustrate the 
unequal heating at the bottom of the 
atmosphere, due to the angle at which 
the rays of the sun reach the surface of 
the earth. The dotted line may be taken 
to represent the outer limit of the atmos- 
phere. 



DISTRIBUTION OF SUN'S HEAT 37 

face in latitudes farther and farther north, and on March 21st they 
are vertical at the equator. Days and nights are then equal every- 
where, because all parallels are cut into two equal parts by the 
circle of illumination (p. 12), and the sun's rays are equally 
oblique in corresponding latitudes north and south of the equator. 
Any latitude in one hemisphere is then receiving the same amount 
of heat as the corresponding latitude in the other hemisphere. 
This condition would be permanent if the axis of the earth were not 
inclined. 

After March 21st, the sun continues its apparent journey north- 
ward until June 21st, when its rays are vertical at the tropic of 
Cancer, 23^° N. The days of the northern hemisphere are then 
longest and the nights shortest, and the rays of the sun are less 
oblique in this hemisphere than at any other time. At this time, 
therefore, the northern hemisphere is being heated more than at any 
other. 

From June 21st to December 2 2d, the sun appears to move so that 
its rays become vertical farther and farther south, and the preceding 
changes are reversed. 

The latitudes where the sun's rays fall vertically range from the 
tropic of Cancer to the tropic of Capricorn; and the sun's rays are, on 
the average, least oblique between these limits. This is why low 
latitudes are, on the whole, warmer than high latitudes. 

The density of the atmosphere also affects the amount and in- 
tensity of the insolation received by the surface of the earth. On 
mountains the less density of the air means more intense sunlight, 
and a greater amount of heat per unit of land surface, than is received 
at sea-level (p. 39). One effect of this is seen in the rapid growth of 
plants on mountains in early summer. 

Distribution of temperature. The temperature of one place is 
not necessarily higher than that of another because it receives more 
heat. The region about the North Pole does not get very warm, 
even when it receives much heat, because much of the heat received 
is used in melting ice and in warming ice-cold water, which is warmed 
very slowly, and flows away as soon as the heating is well begun. 
Mountain tops are also generally cold in spite of the intensity of inso- 
lation there. 

After the heat from the sun has been received by the earth, it is 
re-distributed to some extent, with the general result that the parts 
which get more by insolation share their heat with the parts which 



38 CLIMATIC FACTORS: TEMPERATURE 

get less. The distribution of actual temperature, therefore, differs 
much from the simple distribution which insolation would give. 

There are three ways in which the air receives, loses, and transfers 
heat. These are radiation, conduction, and convection. 

(i) Radiation. The sun always radiates heat, and the surface 
which its rays strike is warmed by absorption of the radiated heat. 
A body need not be glowing hot, like the sun, or like fire, to radiate 
heat. The radiators in our houses radiate heat when they contain 
hot water or steam. The body which radiates heat is itself cooled. 
Thus hot iron soon cools in the air, because it radiates its heat. The 
land warmed by the absorption of heat radiated from the sun during 
the day is cooled by the radiation of its heat at night. The absorp- 
tion of heat by day and its loss by night give variations of temperature 
between day and night. If the day is long and the night short, ab- 
sorption of heat from the sun by day exceeds radiation by night, and 
the land tends to become warmer, as in spring and early summer. 
If the day is short and the night long, radiation of heat will be greater 
than absorption, and the land will become colder, as in autumn and 
early winter. 

(2) Conduction. If one end of an iron poker is put in the fire, the 
other end becomes hot. The heat passes from one end to the other. 
This method of passing heat along is conduction. Any cold body 
in contact with a hot body is warmed by conduction. The hand 
is warmed by conduction when placed on anything which feels warm ; 
it is cooled by conduction when placed on something which feels cool. 
The bottom of the air is warmed by contact with the land (that is, by 
conduction) wherever the temperature of the land is higher than that 
of the air. Conduction from the land to the bottom air has an im- 
portant effect on the temperature of the air just above the ground. 

(3) Convection. When a kettle of water is placed on a hot stove, 
the water in the bottom is heated by conduction, that is, by contact 
with the hot kettle. The heating of the water causes it to expand, 
and when the water in the bottom of the kettle expands, it becomes 
lighter than the water above. The heavier water above sinks and 
pushes the lighter water below up to the top. This movement is 
convection. Another illustration of convection is afforded by stoves, 
fireplaces, and furnaces. A thin sheet of light paper may be held up 
for a moment by the rising air over a hot stove, or even carried up 
if the convection current is strong enough. Again, as the air in a 
chimney is heated, it expands and becomes less dense than the air 



I 






CONVECTION CURRENTS 



39 




Fig. 22. The first rise of air, as a 
result of heating, is due to the expansion 
of the part heated. 




Fig. 23. The permanent heating of 
the air over a region gives rise to per- 
manent convection currents. 



about it. The cooler, denser air about the base of the chimney or 
stove crowds in below the expanded air in the chimney, and .pushes 
it up out of the chimney. Since the air entering the chimney from 
below is being heated and expanded all the time, the up-draught con- 
tinues as long as there is fire. 
Every draught from a chimney 
is an example of convection. 

When the surface of the land 
is warmed by the absorption of 
heat from the sun, it warms the 
air above both by conduction 
and by radiation. The lands 
of low latitudes are heated more 
than others. The heated air 
over the heated land expands. 
If the air in a given region 
were expanded as shown in Fig. 
22, the air at the top of the 
expanded column would flow 
away, much as water would un- 
der similar conditions. After this takes place, the amount of air at 
the base of the column h will be less than the amount at the same level 
outside the heated area, and air from outside the heated column will 
flow in. This inflow will push up the column of expanded air, and 
further overflow above will cause further inflow below. If the heat- 
ing continues, a permanent convection current is established in the 
heated area (Fig. 23). Such movements of air are important not only 
in distributing temperature, but also in causing winds, clouds, and 
storms. 

The atmosphere is heated (1) by the absorption of the sun's rays 
as they come through it, (2) by the absorption of heat radiated from 
land and water, and (3) by conduction from warm land or water to 
the lower air. The amount of heat absorbed by air from the direct 
rays of the sun depends on the distance the rays travel in it, that is, 
on the obliquity of the sun's rays (Fig. 21). When the sun is vertical 
at the equator, its rays pass through about twice as much atmosphere 
in latitude 6o°, and about ten times as much in latitude 85 , as they 
do in latitude o°. The amount of absorption of sun-heat by the air, 
therefore, varies with latitude. About half of it is absorbed by the 
air at the equator, and about four-fifths at the poles, as compared 



4 o CLIMATIC FACTORS: TEMPERATURE 

with the total amount which would reach the earth in those latitudes 
if there were no atmosphere. In general, the amount of heat absorbed 
by the atmosphere is more than 50 per cent of the total amount 
coming to the earth from the sun. 

The heat radiated into the air from below is absorbed by the air 
much more readily than that coming from the sun directly. The 
lower air consequently is heated by radiation from below more than by 
direct insolation. / 

After heat is received from the sun, therefore, it is re-distributed 
by radiation, conduction, and convection. Movements of air (winds) 
and movements of water (especially ocean currents) also distribute 
heat. Without these movements of air and water, the average tem- 
perature of the equator would be much higher than now, and that of 
the poles much lower. These changes would be destructive to many 
forms of life. 

Temperature of land and water. Land is heated by insolation 
four or five times as fast as water, for several reasons : 

(1) A given amount of heat raises the temperature of soil and 
rock more than that of water. 

(2) Water is a good reflector, while land is not; the latter, there- 
fore, absorbs a larger proportion of the heat of the sun 's rays. 

The amount of heat reflected from a water surface increases with increasing 
obliqueness of the sun's rays. At the equator, 40 per cent of the insolation goes 
into heating the water; in latitude 6o°, less than 5 per cent. A familiar result of 
the reflection of heat from water appears in the intensity of sun-burn received on 
water. Snow-covered land and bare white sand reflect heat much as water does. 

• (.3) Land radiates heat more readily than water does. 

(4) Convection movements take place in water as soon as its 
surface is heated. This prevents excessive heating at any one point. 
The land, on the other hand, is without movements of convection. 

(5) There is more evaporation from a water surface than from 
land, other conditions being the same, and evaporation cools the 
surface from which it takes place. A wet soil, receiving the same 
amount of the sun's rays, remains cooler than a dry soil. The hot 
sand of the desert is an example of this effect on the warming of the 
land. 

(6) Light and heat penetrate water, but not soil and rock to 
any great extent. The heat of insolation is therefore distributed 
through a greater thickness of water than of soil. Being confined to 
the surface of the soil, the temperature of the latter is made higher. 



CONTRASTS OF SEASONS 41 

Since the temperature of air tends to be the same as that of the 
surface on which it lies, the presence of land or water is an important 
factor in determining the temperature of the air above. 



Seasons 
In Middle Latitudes 
In middle latitudes, the seasons are four — spring, summer, 
autumn, and winter. Each season has characteristics of its own, 
but each grades into the one which follows. 

In the United States, March, April, and May are commonly called the spring 
months; June, July, and August the summer months; September, October, and 
November the autumn months; and December, January, and February the winter 
months. In the southern hemisphere, spring comes in September, October, and 
November; summer in December, January, and February, and so on. The 
vernal equinox of the northern hemisphere is the autumnal equinox of the southern, 
and the summer solstice of the northern is the winter solstice of the southern. The 
definition of the seasons given above is based on temperature, the warmest three 
months being summer, and the coldest three, winter. The seasons are sometimes 
defined in a different way. Thus spring is sometimes regarded as the time between 
the vernal equinox and the summer solstice; summer the time from the summer 
solstice to the autumnal equinox, and so on. 

Summer and winter temperatures. The summer heat of middle 
latitudes is due (1) to the high altitude of the midday sun above the 
horizon, giving less oblique rays with a shorter path through the 
atmosphere, and (2) to the long days and short nights. More heat 
is received during the long day than is lost during the short night. 
The reverse of these conditions accounts for the cold of winter, though 
during the winter of the northern hemisphere the earth is 3,000,000 
miles nearer the sun than in summer. 

A consideration of Figs. 3 and 9 will make it clear why the seasons are reversed 
in the two hemispheres. One result of this difference of seasons in opposite hemi- 
spheres at the same time is that crops in the middle latitudes of the southern hemi- 
sphere are harvested in our late winter and early spring, when the northern supplies 
of certain things are running low. Hence there is important trade between the two 
hemispheres, places in each hemisphere being benefited because their crops ripen in 
the cold season of the other. 

Warmest and coldest months. Since the northern hemisphere 
receives most heat at the time of summer solstice, and least at the 
time of winter solstice, it would seem at first that these dates, respec- 
tively, should be the times of greatest heat and cold; but this is not the 



42 CLIMATIC FACTORS: TEMPERATURE 

case. Again, since corresponding latitudes in the two hemispheres 
are being heated equally at the time of the equinoxes, it would seem, 
at first, that corresponding latitudes in the two hemispheres should 
have the same temperature at these times; but this, again, is not the 
case. In our own latitudes, for example, March 2 ist (vernal equinox) 
is much colder than September 2 2d (autumnal equinox). 

The explanation of these conditions is found in the fact that 
the temperature of any given place at any given time does not depend 
entirely on the amount of heat received from the sun at that time. 
In our latitudes, the soil, rocks, lakes, and rivers receive more heat 
during the long days of summer than is lost during the short nights. 
At the end of summer, therefore, heat has been stored up in them. 
At this. time of year, the northern hemisphere has a temperature 
higher than that which it would have if it depended entirely on the 
heat received from the sun each day. On the other hand, the tem- 
perature at the time of early spring is lower than that which the daily 
heating would seem to produce, because the cold of the winter just 
past has not been altogether overcome. Some of the snow and some 
of the ice of lakes, ponds, streams, and soils, in middle and high 
latitudes, is still unmelted. The snow and ice keep the lower part 
of the air cool. 

For similar reasons, the summer solstice is not the hottest time 
of year. The time of greatest heat lags behind the time of greatest 
heating. In middle latitudes the lag is about a month; but it is more 
over oceans than over lands, because land is heated and cooled more 
readily than water. For this reason places near bodies of water usual- 
ly have later and colder springs than places not so situated. Under 
such conditions, April in the northern hemisphere may be as cold as 
November. In the same way, the time of greatest cold does not come 
till after the time of least heating. 

In Tropical Latitudes 
The seasons in low latitudes are unlike our own. At the equator, 
the sun 's rays are vertical twice each year — at the times of the 
equinoxes. Twice a year, too, the sun 's rays are vertical 23^2° from 
the equator, once to the north and once to the south. The equator, 
therefore, has two seasons, occurring at the time of our spring and 
autumn, which are somewhat warmer than two other seasons occur- 
ring at the time of our summer and winter. The variations in 
temperature are much less than in middle latitudes, for the length 



CONTRASTS OF SEASONS 43 

of day and night never varies at the equator, and does not vary much 
in any part of the tropics. The angle of the sun's rays, too, varies 
less than with us. At the equator, therefore, there are four di- 
visions of the year, but their differences of temperature are slight. 
Toward the margins of the tropical zone, the variations of tem- 
perature are greater than at the equator, but far less than in middle 
latitudes. In much of the tropical zone, wet seasons alternate with 
dry ones, and in such places, differences in moisture are more im- 
portant than differences in temperature. 

In High Latitudes 

In high latitudes, the seasons are still different. About latitude 
6o°, for example, the differences in the seasons are similar to those 
of the central part of the United States, except that they are greater, 
because of the greater variation in the length of day and night. In 
latitude 63 , the longest day of summer and the longest night of 
winter are about 20 hours each, as compared with a little over 15 
hours in latitude 40 . The long nights of winter in latitude 63 
mean much lower temperatures than in latitude 40 at that season. 
On the other hand, the long hours of sunshine in summer make 
it possible, in favored localities, to grow Crops as far north as latitude 
6o°, even where it is only four months from snow to snow. 

In latitude 75 N., which may be taken as typical of polar regions, 
there are four natural divisions of • the year, one (summer) when 
daylight is continuous, one (winter) when darkness is continuous, 
one (spring) when there is alternating day and night, with the days 
lengthening, and one (autumn) when there is alternating day and 
night, with the nights lengthening. The lengths of the seasons 
defined in this way are not the same. 

There is a common notion that in polar regions there is a day of six months 
and a night of six months each year, but this is not correct. There is a six-month 
day and a six-month night at the poles only. In latitude 78 , about half way between 
the pole and the polar circle, there is continuous daylight and continuous darkness 
for periods of about four months each. In latitude 70 the periods of continuous 
darkness and of continuous light are two months each, and so on down to 24 hours 
at the polar circle. 

Though the name summer may be applied to one part of the year 
in high latitudes, places north of latitude 6o°-65° are not warm enough 
in summer for the growth of cereal crops. Vegetation is confined to 
grasses, stunted shrubs, lichens, and mosses. 



44 CLIMATIC FACTORS: TEMPERATURE 

Relation of Temperature and Altitude 

High altitudes are colder than low levels in the same region, 
(i) because the air is thinner, and (2) because it contains less water 
vapor, carbon dioxide, and dust. For these reasons it absorbs less 
heat from the direct rays of the sun, and less of that radiated from 
below. The temperature of the air on top of a mountain may be 
much lower than the temperature of the air at its base, in spite of the 
fact that insolation is much greater in the former position. 

The average decrease of temperature is about i° F. for each 330 
feet of rise, or 16 for each mile, for the altitudes where observations 
have been taken. One mile of ascent, therefore, means about the 
same decrease of temperature as a journey of 1,000 miles (about 15 
of latitude) toward the poles. Tropical highlands, like those of 
Mexico or Bolivia, in latitudes 18 to 19° N. and S. respectively, 
are cooler than some places at sea-level in middle latitudes. For 
this reason, some countries in the tropics can produce not only 
tropical crops, but also those characteristic of other regions, and by 
living at the higher elevations, the people may escape the uncomfort- 
able heat of tropical lowlands. In middle latitudes also vegetation 
varies with the altitude. Thus, in the low mountains of Pennsylvania, 
the ridges bear coniferous trees (pines, etc.), sugar maples, and similar 
types, while the valleys between have the honey locust, gum, and 
walnut, which need a warmer climate. 

The low temperatures of certain mountains and high plateaus of 
the middle zones do not favor dense populations. On the other hand, 
the cool climates of various high lands in the tropics have favored 
white settlements. During the hot summer months the capital of 
India was transferred each year from Calcutta (the capital until 
191 1), near sea-level, to Simla in the Himalayas, at an elevation of 
7,000 feet. Certain elevated places in the Philippines, like Baguio, 
the summer capital, will have increasing importance as health and 
pleasure resorts during the hot period. 

The difference in vegetation and in human conditions between 
the sunny and shady slopes of mountains is striking in many cases. 
Thus at a place near Zermatt, in the Alps, barley and rye are grown 
on a sunny southern slope 6,900 feet above sea-level, while a few 
hundred yards away, northern slopes, even below the level of the 
grain fields, have arctic-alpine vegetation and snow-banks. In some 
of the valleys in the Alps, most of the people live on the sunny slopes. 



CHARTING TEMPERATURE DATA 45 

Where mountains are covered by snow throughout the year, their surfaces are 
never warmed above a temperature of 32° F. , the melting temperature of snow. All 
the heat received beyond that necessary to raise them to this temperature is spent 
in melting and evaporating snow, not in raising the temperature of its surface. 
Yet in spite of the freezing temperature, travellers over the snow-fields may be 
sun-burned, as if exposed to midsummer sun at lower altitudes. Part of this effect 
is due to the greater intensity of insolation at higher altitudes, and part of it to the 
fact that snow reflects heat much as water does (p. 40). 



Representation of Temperature on Maps 

It is important to have some means by which temperatures in 
different places and at different times may be studied readily. For 
large areas it is most convenient to have the temperatures shown on 
maps. Maps showing temperatures are thermal maps. On such maps 
temperatures and their distribution commonly are shown by lines, 
each of which connects points having the same temperature. Such 
lines are isotherms, and maps showing isotherms are isothermal maps. 
A line connecting places having the same average annual temperature 
is an annual isotherm. Lines connecting places of the same average 
seasonal or monthly temperature are seasonal or monthly isotherms. 

Fig. 24 shows annual isotherms. The map does not give exact 
average temperatures for places between the lines, but tempera- 
tures for such places can be estimated from the map. At the 
extreme north there is the isotherm of o° F., which barely touches 
North America. The average annual temperature of places on 
this line is o° F. The isotherm of io° F. lies south of the isotherm 
of o° F. The average temperature of places between these two iines 
is more than o°, and less than io°. South of the isotherm of io° 
follow, in order, the isotherms of 30 , 50 , 6o°, and 70 . The lowest 
isotherm shown on the chart in the southern hemisphere is that of 
30 , lying south of all lands except Antarctica. The latitude of this 
isotherm corresponds nearly to the latitude of the isotherm of 30 
in the northern hemisphere. Next toward the equator from 
the southern isotherm of 30 is the isotherm of 50 , followed by those 
of 6o° and 70 . Thus the map shows a relation between latitude 
and annual temperatures, the highest temperatures being near the 
equator. 

Annual isotherms do not show all we may want to know about 
the temperature conditions of a place. An annual isotherm of 50 F., 
for example, does not tell us whether the temperature is about 50 F. 



4 6 



CLIMATIC FACTORS: TEMPERATURE 




~ <u 



ISOTHERMAL CHARTS 47 

all the time, or whether it is 8o° F. in summer and 20 in winter. 
Seasonal and monthly isotherms are of more significance in con- 
nection with crops, and give a better idea of the temperature condi- 
tions of a place. This may be illustrated by the fact that the annual 
isotherm of New York is about the same as that of southern England, 
while the summer isotherm of the former place is more than io° 
warmer than that of the latter. Since summer temperatures are the 
most important for crops and for many human activities, the difference 
of more than io° in that season is enough to make New York and 
southeastern England quite unlike in many respects. Again, San 
Francisco and St. Louis have the same mean annual temperature; 
but the January average is only io° lower than the July average at San 
Francisco, while it is 45 lower at St. Louis. Range of temperature is, 
therefore, important. The annual range of temperature for Quito, 
Ecuador, is i° F. ; that is, the warmest month is only about i° warmer 
than the coolest. For San Diego, CaL, the range is 16 F.; for St. 
Paul, Minn., 6o°; for Yakutsk, northeastern Siberia, ioo°. 

Fig. 25 shows the isotherms for January. On this chart corres- 
ponding isotherms are farther south than on the chart of annual 
isotherms. Thus the isotherm of o° F. ( — 17.78 C.) in the northern 
hemisphere runs through central Asia, instead of lying north of it, 
and the isotherm of 6o° is everywhere south of latitude 40 , instead 
of being partly north of it, as in Fig. 24. At this time of the year, 
the sun is shining vertically south of the equator. This seem c to be 
a sufficient reason for the change. 

Fig. 26 shows the isotherms for July. All isotherms are farther 
north than the corresponding ones on either of the other charts. Thus 
the isotherm of 50 in the northern hemisphere is about where the 
isotherm of 20 was in January (Fig. 25). 

Comparing Figs. 2-5 and 26, it is seen that the difference of tem- 
perature between January and July is much greater in high latitudes 
than in low. Thus in the southern part of Hudson Bay there is 70 
difference between January and July; at Lake Erie, about 45 ; in 
Florida, about 20 ; and near the equator in South America, less than 
io°. The same charts show that the difference is greater in the 
interiors of continents than on coasts or over the sea in the same 
latitude. Thus in the interior of North America, west of Hudson 
Bay, the difference is about 8o°, while on the coast of Alaska it is 
only about 30 . These conditions bear out the conclusions already 
reached, (1) that the difference in the amounts of heat received at 



4 8 



CLIMATIC FACTORS: TEMPERATURE 




ISOTHERMAL CHARTS 



49 




bo 



5 o CLIMATIC FACTORS: TEMPERATURE 

different seasons is greater in high latitudes than in low latitudes, and 
(2) that land heats and cools more readily than water. 

The courses of isotherms. (1) The isotherms are roughly 
parallel to the parallels of latitude. Some of them are very irregular, 
it is true, but the east-west direction is the most common one. This 
shows some relation between the courses of isotherms and latitude; 
but since the isotherms do not follow the parallels exactly, it is clear 
that latitude is not the only thing which determines their position. 

(2) Figs. 25 and 26 show that the isotherms are least crooked 
where there is little land, and most crooked where there is much land. 
This suggests that the land and water have something to do with 
their positions. There are various irregularities in the isotherms on 
land that do not appear on the sea. Thus, on the January chart, 
there is an area in South Africa, and another in Australia, surrounded 
by the isotherm of oo°, and in July there are similar areas in North 
America, northern Africa, and southern Asia. All of these areas are 
on land. These facts tend to confirm the conclusion that the sea 
and the land influence the position of the isotherms. 

Following this idea further, it is seen that some of the isotherms 
of January bend somewhat abruptly toward the equator in passing 
from water to land, and toward the pole in passing from land to 
water. Thus the isotherm of 30 in the northern hemisphere turns 
to the south where it reaches North America, and again on the coast 
of Europe. In the southern hemisphere, the isotherms of 8o° and 70 
make abrupt turns at the west coast of Africa, and the isotherm of 
70 near the west coast of South America. These bends at the coasts 
give further support to the conclusion that the distribution of land 
and water has something to do with the position of isotherms. 

It has been noted already (p. 40) that the land is heated and 
cooled more readily than the sea, and is therefore colder in winter 
and warmer in summer. The January isotherm of 30 in the northern 
hemisphere bends toward the equator in crossing the northern con- 
tinents, because the land is cooler than the water in the same latitude, 
at this time of year. In the southern hemisphere, where it is summer, 
the isotherms bend toward the pole on reaching the land, because the 
land is warmer than the sea in the same latitude. 

The chart of the July isotherms leads to the same conclusion. 
On this chart, isotherms crossing the northern continents bend 
poleward on the land, while those crossing the southern continents 
bend equatorward. This is the season when the lands of the northern 



ISOTHERMAL CHARTS 51 

hemisphere are warmer than the seas of the same latitude, and when 
the lands of the southern hemisphere are cooler than the seas. 

The irregularities of the isotherms of the northern hemisphere 
in July are much greater than those of the southern hemisphere 
in January (summer in the southern hemisphere). This is prob- 
ably because there is much more land in the northern hemisphere 
than in the southern, and the larger land areas have a greater effect 
on the isotherms than the smaller ones. 

(3) There are some features of the isothermal lines which are 
not explained by latitude, or by the distribution of continents and 
oceans. Thus the bends of the isotherms are not as pronounced on 
the east sides of the continents as on the west. This is shown by 
Figs. 25 and 26. Again, traced eastward, the January isotherm of 50 
bends southward near the west coast, of North America more sharply 
on the land, while on the eastern side of the continent it bends north- 
ward on the sea, not on the land. Such peculiarities may be explained 
by the winds. The prevailing winds in the middle latitudes of North 
America are from the west. These winds tend to carry the tempera- 
ture of the sea (warmer in winter) over to the land on the western 
side of the continent (Fig. 25), and the temperature of the land 
(cooler in winter) over to the sea, on its eastern side. This explains 
the bends of the isotherm of 50 , for example, near the coasts in the 
northern hemisphere in January. Coastal lands on the western sides 
of continents in middle latitudes tend to have temperatures like 
those of the neighboring ocean. 

(4) The great bend in the January isotherm of 30 in the North 
Atlantic is due to a northeastward movement of warm ocean water 
in the direction of the pronounced loop of the isotherm. Ocean 
currents are therefore a fourth cause of the irregularities of isotherms. 
The amount of heat carried northward by the ocean currents of 
the Atlantic and Pacific is very large. It has been estimated that 
the temperature of the British Isles and Norway is raised several 
degrees by the warm poleward movement of waters in the North 
Atlantic. The temperature of the land is raised by this water, 
because the air over the warm ocean water is warmed and then 
blown over the land. 

The milder climate of northwestern Europe, as compared with 
northeastern North America, is not due wholly to the northward 
movement of warm water. Even without such movement, the 
climate of northwestern Europe would be somewhat warmer in 



52 CLIMATIC FACTORS: TEMPERATURE 

winter than that of northeastern North America in the same latitudes, 
because the ocean, from which the winds of winter blow to north- 
western Europe, still would be warmer than interior North America, 
whence the prevailing winds blow to the eastern coast of that conti- 
nent. 

There are some other less important causes of irregularities in 
the isotherms. Thus a basin region, shut in by mountains, gets 
hotter in summer than a region not so surrounded. Again, there 
is less evaporation from a dry surface than from a moist one, and 
since evaporation cools the surface, a dry surface will be warmer 
than a moist one, if other conditions are the same. The color of the 
soil, the presence or absence of vegetation, and other things, also 
affect the absorption and radiation of heat. The high temperature 
in the southwestern part of the United States in July (Fig. 26) is 
accounted for partly by the fact that the region is somewhat shut 
in by mountains, and has a dry, sandy soil but scantily covered with 
vegetation. 

Altitude affects temperature, as already explained, but isother- 
mal charts show no relation between isothermal lines and surface 
relief. The reason is that isothermal lines are represented on maps 
as if they were at sea-level. This is done by making allowance for 
altitude at the average rate of i° F. for about 330 feet. Thus if 
the temperature of a place at an altitude of 3,300 feet is 6o°, it is 
put down on the chart as 70 (6o°+io°). Isothermal charts, there- 
fore, are intended to show the temperature as it would be if the land 
were at sea-level. 

Ranges or Temperature 

Daily range. The temperature of a day when the sun shines is 
generally higher than the temperature of the night. The difference 
is as much as 40 or 50 F. in many places, and as much as 70 in 
some. The daily range of temperature of air over the ocean is much 
less than over the land; other things equal, less at high altitudes than 
at low altitudes, and less in moist regions than in dry ones. 

The greatest importance of daily range of temperature is in con- 
nection with the growth of crops. Since many plants, including 
many food plants, are injured or killed by a freezing temperature 
(commonly called " frost"), they are restricted to regions where 
the temperature during the growing season does not fall as low as 
32 F. 



FROSTS AND CROPS 53 

The danger of "frost" at night varies with local conditions, as (1) altitude, (2) 
exposure, (3) character of the soil, and (4) nearness to water bodies. Valley 
bottoms have frosts earlier in the autumn than neighboring hillsides, because the 
colder, heavier air moves down slopes and accumulates in low places. The great 
coffee plantations of Sao Paulo, Brazil, the olive and fig trees of Italy and Istria, 
the orange and peach orchards of California, and the vineyards in the Rhine Valley 
and in the south of France are found largely on hillsides. 

Northern slopes are more subject to frosts than southern ones, because the 
latter are warmed more by day and hence must cool more at night before a freezing 
temperature is reached. Sandy soils are more liable to frost than clay soils situated 
similarly, for the reason that clay soils are usually wetter. The air above them 
contains more moisture, and so cools less readily. The condensation of moisture 
sets free heat and so checks further cooling. Of two crops on the same farm, one 
on clay soil, the other on sandy soil, the one may be untouched by "frost" on a 
night when the other is injured seriously. Places near water bodies, and in their 
lee (i. e., on the side toward which the wind blows from the water) have their 
temperatures influenced by the temperature of the water. Frosts at night in 
autumn are somewhat less common in such situations. The effect of large water 
bodies is seen in the location of important fruit districts on the lee (east) shore of 
Lake Michigan, and on the lee (southeast) shores of Lakes Erie and Ontario. A 
similar influence affects the important fruit and trucking industry of the peninsula 
between Delaware and Chesapeake bays. Frosts during the growing season are, 
in some cases, so destructive as to amount almost to national dioasters. A frost 
in the late spring, after corn is well started, or in early autumn, before it is ripe, 
may reduce the crop of good corn by millions of bushels. When freezing tem- 
peratures extend into regions usually free from them, they do great damage to 
fruit, as to orange groves in Florida. A disastrous frost in December, 1894, 
affected this region. 

The economic importance of frost is so great that the federal government has 
given much attention to methods for protecting perishable crops, and one of the 
most valuable services of the Weather Bureau is the sending out of frost warnings 
which give the farmers of the country anywhere from 6 to 24 hours to make prepara- 
tion for protection. In this way, millions of dollars' worth of crops are saved every 
year. The cost of protection for several consecutive nights may not equal 1 per 
cent of the value of the crop saved. 

The average daytime temperature during the growing season, 
and the number of days when the temperature is above a given point, 
are important matters, since most plants require, for growth, a tem- 
perature well above 32 F. 

The daily range of temperature is also important to human beings, 
especially where the days are hot. Thus in desert regions the heat 
of midday may be much above ioo° F.; but night temperatures in 
the same place may be as low as 45 or 50 F., making restful sleep 
possible. 

It is the daily range of temperature which accounts partly for the 
invigorating effects of a vacation in the mountains. 



54 CLIMATIC FACTORS: TEMPERATURE 

Seasonal range. The seasonal range of temperature is affected 
by (i) latitude, (2) position with reference to land and sea, (3) pre- 
vailing winds, and (4) the presence of snow. 

(1) The seasonal range of temperature increases with the latitude 
(compare Figs. 25 and 26), because the yearly variation of insola- 
tion increases with the latitude. San Diego and St. Paul (p. 47) are 
examples. In latitudes higher than that of St. Paul the range is still 
greater. 

(2) Islands and coasts have a smaller range than continental in- 
teriors in the same latitude, because the range of sea temperature is 
less than the range of land temperature (Figs. 25 and 26). St. Louis 
and San Francisco (p. 47) are examples. 

(3) A coast to which the prevailing winds blow from the ocean 
has a less range of temperature than a coast to which the prevailing 
winds blow from the land. Thus the range of temperature is less 
on the Pacific coast of the United States than on the Atlantic in the 
same latitude (Figs. 25 and 26), the winds being chiefly from the west 
in both cases. 

(4) The presence of snow during the warm season, as in high 
latitudes and high mountains, prevents a high temperature, even 
though insolation is strong (p. 45). In the cold season, snow also 
tends to reduce the temperature of the lower air by reflecting a 
certain amount of insolation which might otherwise help to warm 
the land, and so the layers of air in contact with it. On the other 
hand, snow lessens the range of temperature of the soil beneath it, 
for snow checks radiation from the soil, and prevents it from being 
warmed by the direct rays of the sun. By preventing alternate freez- 
ing and thawing of the soil, snow is important to many plants, as, for 
example, winter wheat and clover. 

Importance of temperature ranges. The annual range of tem- 
perature affects all industries connected with the soil. In general, the 
temperature of most importance to vegetation is the lowest or mini- 
mum temperature. For example, the palm-tree does not thrive where 
frosts occur; hence its natural distribution is limited to places where 
the lowest temperature of the year is above 3 2 F. Peach-trees, unless 
protected, are injured by temperatures below — 15 F. if they last long, 
and if such temperatures come often, peaches cannot be grown. For 
most crops, as corn, cotton, rice, tobacco, sugar cane, fruits, and 
vegetables, the length of time without freezing temperatures (the 
growing season) is a critical factor affecting their distribution. 



QUESTIONS 55 

Unseasonably low temperatures may destroy crops not only for 
that year, but in some cases for years to come. Thus, early in 
October, 1906, a temperature which was in places 13 below freez- 
ing killed hundreds of thousands of peach-trees in western Michigan. 
Peach-trees stand much lower temperatures in winter without injury, 
but this freezing temperature came before the trees were ready for it. 



Questions 

1. From what sources, besides the sun, does the earth's surface receive heat? 

2. What temperature Centigrade corresponds to 45 F.? To — 45 F.? 

3. Make a rule for changing degrees F. to degrees C, and vice versa. 

4. The earth is probably not getting warmer, in spite of the fact that it is 
receiving heat all the time from the sun. Why? 

5. On June 21st, in latitude 40 N., which would receive more heat, (1) a 
horizontal surface, or (2) a vertical surface of equal area facing south? On Sep- 
tember 21st? Draw diagrams to illustrate answers. 

6. For each of the various ways of heating a house, by (1) open fire, (2) stoves, 
(3) hot-air furnace, (4) steam, and (5) hot water, which process of heat distribution 
(radiation, convection, conduction) is most important? 

7. In what way may satisfactory ventilation of a heated room be secured? 

8. Why does snow mixed with dirt melt more rapidly than clean snow? 

9. How does a lake tend to modify the temperature of the surrounding land 
by day? By night? In summer? In winter? Explain each. 

10. Explain each important curve in the January isotherm of io° F., northern 
hemisphere (Fig. 25). 

11. (1) Compare and contrast the average January and July temperatures on 
the east and west coasts of the United States at the fortieth parallel (Figs. 25 and 
26). (2) Explain the differences. 

12. Why are the average annual temperatures over tropical lands higher than 
those over tropical seas? 

13. Where do the highest July temperatures occur (Fig. 26)? Why there? 
The lowest January temperatures (Fig. 25)? Why? 

14. Compare and contrast the seasonal range of temperature in the middle 
latitudes of the two hemispheres (Figs. 25 and 26). Why the difference? 

15. Of two cities, St. Paul and Key West, one has an average daily range in 
temperature twice as great as the other. Which has the greater? Reasons? 

16. Why is the average annual temperature higher in cities than in the sur- 
rounding country? Why is the daily range of temperature smaller in cities than 
in the country? 

17. What is the length of the growing season in mountains, as compared with 
neighboring plains? Why? 



CHAPTER VI 
CLIMATIC FACTORS: MOISTURE 

Importance of Atmospheric Moisture 

We cannot see or smell or feel water vapor, though air with much 
■water vapor has a different feeling from air with little. 

The presence of vapor in the air may be proved in various ways. 
Drops of water often appear on the outside of a pitcher of ice- water 
in summer, and cold window panes often have "steam" on them in 
winter. In each case the water came from the air. Water vapor 
often condenses into water on the surface of dust particles in the air. 
Great numbers of these water-covered particles high in the air form 
clouds, from which rain may fall if the drops become heavy enough. 

Water vapor is lighter than dry air; that is, a cubic foot of it 
weighs less than a cubic foot of dry air at the same temperature and 
under the same pressure. Water vapor in the air displaces some of 
the oxygen and nitrogen, and therefore makes the air lighter. 

The moisture of the air is no less important than oxygen and 
carbon dioxide to animals and plants, for without it no life could 
exist on the land. It furnishes the rain and the snow which supply 
all springs and rivers, and it serves a most important function in 
connection with temperature, as already stated (p. 32). It increases 
the average temperature at the bottom of the atmosphere, and reduces 
the extremes of heat and cold which would exist if the air were alto- 
gether dry. This is shown by the fact that dry regions have greater 
ranges of temperature than moist ones in similar latitudes and alti- 
tudes. Moisture from the air also acts with the oxygen and with 
changes of temperature in the breaking up of rocks and the formation 
of soil from them (p. 162). 

Evaporation 

Sources of water vapor. Water left in an open dish disappears 
slowly, and muddy roads and wet pavements become dry after the 
rain ceases. The water evaporates; that is, it disappears in the form 

56 



SOURCES OF WATER VAPOR 57 

of vapor. Vapor is passing from all moist surfaces into the air all the 
time. Evaporation also takes place from snow and ice, even at tem- 
peratures far below that of melting. Explorers in Arctic regions 
say that moist garments left on the snow during a clear night may be 
dry in the morning, even with a temperature of — 40 F. The mois- 
ture in the garments freezes, and the ice evaporates. 

All animals breathe out water vapor into the air. This is seen 
'on very cold days when the water vapor of the breath condenses, and 
so becomes visible. The water breathed out into warm air is not 
seen because it does not condense. Growing plants also give out 
moisture, the amount, in many cases, being very great. 

A thrifty sunflower plant, during its life of 140 days, gave off 125 pounds of 
water. Grass was found to give off its own weight of water every 24 hours, in hot 
weather. This meant, where the measurement was made, 6}4 tons per acre, or a 
little more than a ton for a lot 50 feet by 150 feet. A birch-tree, with some 200,000 
leaves, was estimated to give off 700 to 900 pounds on a hot summer day, but 
much less on a cool day. 

Water vapor also enters the air from all active volcanoes (p. 191). 
The oceans, however, are the great evaporating pans from which most 
water vapor comes, and but for them the waters of the land would all 
be dried up in the course of time. 

Water is in constant circulation in the air. The circuit which it 
makes is somewhat as follows: (1) It is evaporated from the ocean 
(and all moist surfaces) ; (2) as vapor, it is diffused and blown over the 
land, where some of it (3) is condensed and falls as rain or snow. A 
part of the rain which falls on the land returns directly to the sea 
through rivers, a part sinks into the ground, and another part is evap- 
orated again. About half the water vapor of the air is below an 
altitude of 6,500 feet. Its abundance near the bottom of the air 
is one reason why the lower air is warmer than that above (p. 44). 

On the average, 30 to 40 inches of rain fall each year on land; that 
is, enough to make a layer 30 to 40 inches in average depth if spread 
out over all the land. The amount of water evaporated from the 
oceans each year is about the same as that which falls from the air. 
If precipitation (rainfall and snowfall) on the oceans is equal to that 
on the lands, square mile for square mile, and if all the water of the 
rain and snow came from the .oceans and was not returned to them, 
the oceans would be dried up in 3,000 or 4,000 years. If an amount 
of water equal to all the rainfall of a year were evaporated from 
lakes, they would probably all be dried up in less than a year. 



58 CLIMATIC FACTORS: MOISTURE 

Rate of evaporation. The principal conditions affecting the 
rate of evaporation are (i) the amount of water vapor already in the 
air, (2) the temperature of the surface and the air over it, and (3) the 
strength of the wind. At a given temperature, the less the water 
vapor in the air, the more rapid the evaporation from a water surface. 
Raising the temperature of air from 30 to 50 F. doubles its capacity 
to hold water vapor, and hence increases the rate of evaporation. 
Air moving 10 miles an hour willevaporate four times as much water 
as still air, other things being equal. 

Effect of evaporation on temperature. Evaporation cools the 
surface from which it takes place. If the hand be moistened, it feels 
cool as the water on it evaporates, and the faster the evaporation, 
the more distinct the cooling. Moist clothing seems cooler in wind 
than in still air, even when the temperature is the same, because 
wind increases evaporation. For the same reason, a day in summer 
when the wind is blowing seems cooler than a calm day when the 
temperature is the same. 

Evaporation from forested regions in moist tropical lands is so great that the 
temperature there is much lower than would be expected from the insolation. The 
slight evaporation from dry regions is one reason why they are so hot in the sunny 
days of summer. Dry heat is less uncomfortable than damp heat because the 
increased evaporation from the human body in a dry region reduces its temperature. 
The hot, dry air of a furnace room causes far less discomfort than the less hot, damp 
air of a green-house. On the other hand, moist air at o° F. seems much cooler than 
dry air at the same temperature. 

Sensible temperature. The difference between temperature as 
it seems (sensible temperature) and temperature as it is (shown by the 
thermometer) is often great. Thus, observations in Death Valley, 
California, showed a maximum air temperature of 122 on five days, 
but the sensible temperatures ranged from 73 to 77 F. Yuma, 
Arizona, with an average temperature of 92 in July, does not seem 
so hot as Savannah, with a temperature of 82 , and but little hotter 
than Boston, with a temperature of 72 . This is because the air at 
Yuma is very much drier than that at Savannah or Boston. Sensible 
temperatures bear a very important relation to sunstroke and heat 
prostration, both of which are almost unknown in our dry south- 
western states, but are of frequent occurrence along the less hot but 
more moist eastern coast. 

Saturation. The amount of water vapor in the air varies greatly 
from place to place, and from time to time at the same place. When 



HUMIDITY AND LIFE 59 

there is as much water vapor in the air as there can be under existing 
conditions, it is said to be saturated. A cubic foot of air at o° F. is 
capable of containing }4 grain of water vapor; at 30 , about 2 grains; 
at 6o°, 5 grains; at 8o°, n grains; and at 90 , nearly 15 grains. Thus 
the higher the temperature the greater the amount of water vapor 
necessary for saturation. 

Humidity 

Absolute and relative humidity. The amount of moisture 
which the air contains is its absolute humidity. The percentage of 
moisture which air contains at any temperature, compared with 
what it might contain at that temperature, is its relative humidity. 
If a cubic foot of air at 30 F. contains 2 grains of water vapor, it 
is saturated, and its relative humidity is. 100 per cent. If the tem- 
perature is raised to 6o° F., its capacity for water vapor is increased 
from 2 grains to 5 grains, and its relative humidity is then 40 per cent. 
On the other hand, if air at 8o° F., containing 5 grains of water vapor 
(relative humidity about 46 per cent), were cooled to 6o° F., the 5 
grains would mean saturation for that temperature. Air is said to 
be "dry" when its relative humidity is low, and " moist" when its 
relative humidity is high. Thus 5 grains of water vapor in air at 90 
F. means dry air (humidity 3$), while the same quantity of water 
vapor in air at 6o° F. means damp air. The air over damp England 
and that over the dry Sahara, for example, may have the same actual 
amount of water vapor per cubic foot. 

The average relative humidities in the United States range from 80 along the 
coasts to less than 40 in some parts of the southwest. Areas where the relative 
humidity is 35 or less are essentially desert, and areas where it is less than 50 are 
distinctly dry. The average relative humidity of air over the land is probably 
about 60; that over the ocean about 85. In that part of the United States where 
ordinary farming can be carried on without irrigation, the relative humidity is, as 
a rule, more than 65. 

Importance of relative humidity. Corn, wheat, and rye, 
require, respectively, about 14, 10, and 8 inches of water during their 
growing seasons. If the total rainfall of a given place is 18 inches in 
that time, any one of the crops would seem to have enough. But if 
the relative humidity is very low, evaporation is rapid. In this case 
18 inches of rain may be necessary to grow rye. 

Relative humidity has important effects on the human body. Moisture is 
all the time being evaporated from the skin and lungs. High humidity checks 
evaporation, and this seems to be one cause of certain diseases in moist tropical 



60 CLIMATIC FACTORS: MOISTURE 

regions. Low humidity increases evaporation from the body, and this is, on the 
whole, stimulating. Sudden changes from low to high humidity, especially when 
associated with sudden changes of temperature, such as occur when one goes out 
from a warm house in winter, probably favor diseases of the breathing organs (cold, 
etc.), so frequent at that season. 

High relative humidity hastens the decay of food, especially meat; hence 
many foods cannot be kept long in warm, moist places. This is perhaps one 
reason why little meat is used in tropical countries. Unprotected iron wares rust 
rapidly in damp air. The damp air of the coast of Maine prevented the successful 
development of the sardine industry, in spite of a law providing that the drying 
should be done only on "dry clear days," until a special method of curing the fish 
made it possible to compete with the French product dried out of doors. In some 
places meat is dried in the air, giving the so-called "jerked beef." Even "burial" 
of the dead may be on high platforms in regions where dry air quickly mummifies 
the body. 

Extreme dryness and the evaporation which goes with it cause wood to shrink, 
warp, and crack to such an extent that boxes which were strong fall apart. Goods 
to be shipped far through a very dry region need special preparation, and even 
railroad cars have to be of steel to withstand the effect of desert dryness. Humidity 
is so important in textile industries, as in spinning cotton, that the early centers 
of cotton manufacture tended to develop in damp regions. In many mills, special 
devices are now used to maintain uniform humidity. 

Dew point. If saturated air (p. 59) is cooled, some of its water 
vapor is condensed (becomes liquid). The temperature at which it 
begins to condense is the dew point. Air may be brought to the dew 
point in various ways : (1) It may be blown where the temperature 
is lower, as to a higher latitude or altitude; (2) it may be cooled by 
having cooler air brought to it, as by a cold wind; (3) it may be cooled 
by radiation, or (4) by expansion, as when it rises. 

The temperature of the dew point is not fixed, but is influenced 
by the amount of water vapor in the air, as already explained (p. 59). 
If air at 8o° F. contains 5 grains of vapor per cubic foot, its dew point 
will be reached when it is cooled to 6o° F. ; but if the amount of water 
vapor in air at 8o° F. is only 2 grains per cubic foot, the dew point 
would not be reached until it had been cooled to 30 F. 

If the temperature of condensation is above 32 , the vapor con- 
denses into liquid water, which at first takes the form of droplets, 
such as those of which fog is made. If the temperature of condensa- 
tion is below 3 2 , particles of ice form as the vapor condenses. 
They may be the beginnings of snowflakes, or they may be particles 
of frost. The condensation of water vapor sets free an amount of 
heat equal to that absorbed in its evaporation. This heat checks 
the cooling, a fact of importance where the temperature of condensa- 



FORMS OF CONDENSED VAPOR 61 

tion is near 3 2° F., and where continued cooling would bring the 
temperature to the freezing point. 

Dew and frost. In the clear, still nights of summer and autumn, 
the temperature of the surface of the land, cooling by radiation, 
often becomes lower than the dew point of the air above. Moisture 
then condenses on the surface. Such moisture is dew if the tempera- 
ture of condensation is above 32 . The water which condenses on 




Fig. 27. Fog over the lowlands, as seen from Mount Wilson, California. (Ellerman.) 

the outside of a pitcher of ice-water (p. 56) is dew, just as much as 
that which forms on grass blades. Dew does not fall, but condenses 
on the surface of solid objects. When the temperature of the dew 
point is below 32 F., the moisture which condenses on solid objects 
condenses as ice particles, or frost, instead of dew. 

Dew is more likely to form on still nights than on windy ones, because wind 
tends to move away air which is approaching its dew point, supplying other air in 
its place, and the incoming air may be warmer or drier than that which moved on. 
Dew is more likely to form on clear nights than on cloudy ones, because radiation 
and cooling are greater when there are no clouds. This association of dew with 
clear skies led the ancients to believe that dew came from the stars. 

Fog and cloud. The condensing of water vapor in the air into 
droplets makes fog (Fig. 27) if the droplets are in the lower part of 



62 CLIMATIC FACTORS: MOISTURE 

the atmosphere at a temperature above 32 F. It makes ice particles, 
or frost, if the temperature is below 32 F. Water droplets and ice 
particles in large numbers make clouds if formed well above the 
bottom of the atmosphere (Figs. 28-31). Fog may be said to be 
cloud resting on the surface of land or water. The droplets of water 
forming fog and cloud are very small, many of them not more than 
V3000 of an inch in diameter. 

Fogs are formed in many cases where the moist air over warmer water (e.g., 
a warm ocean current) blows over a colder surface of water or land. They often 
form in valleys at night (Fig. 27), especially in autumn, when the night tempera- 
tures are much lower than those of the day. The cooler air settles in the valleys, 
and the air there is more likely to be brought to the dew point than that over the 
uplands. Fogs occur more frequently in large cities than in the nearby country, 
apparently because the large numbers of solid particles poured into the air 
in the form of smoke favor condensation. In London, fogs increased as more 
coal was burned until the "smoke nuisance" was partly stopped; then the fogs de- 
creased. In other places, also, doing away with smoke has nearly put an end to fogs. 

Fogs interfere with all kinds of traffic. They are the most common cause of 
disasters at sea, as in the collision of the French steamship La Burgogne with an 
iceberg in the North Atlantic, as a result of which more than 600 lives were lost. 
Coastwise traffic, as in Nantucket Sound, or traffic in river harbors, as at Philadel- 
phia, is kept at a standstill for days at a time by fogs. Fogs also have caused 
many railway accidents. 

In some places where fogs are frequent and heavy, they may serve as a 
source of moisture. The distribution of the redwood tree in California corresponds 
closely to the zone over which fogs extend inland. Along some African rivers the 
moisture from valley fogs, always drifted one way by the winds, causes heavier 
vegetation on one bank than on the other. Attempts by men to utilize the moisture 
of fogs have never proved very successful. 

Forms of clouds. Clouds take many forms. (1) Cumulus clouds 
are thick, with upper surfaces somewhat dome-shaped, and with 
irregular and fleecy projections. Their bases are nearly horizontal 
(Fig. 28). They are formed from the water vapor in ascending con- 
vection currents, and their level bottoms seem to mark the altitude 
at which condensation takes place as the air rises. Their bottoms 
are usually somewhere from 1,800 to 4,000 feet above the land, but 
the tops may rise three or four miles higher. They appear, especial- 
ly in clear, hot weather, in mid- or late-forenoon, after insolation has 
established convection currents. They attain their greatest size 
at about the hour of maximum heat. As evening approaches they 
commonly grow smaller and disappear. (2) Stratus clouds are hori- 
zontal sheets of cloud, often not more than 1,000 feet above the earth. 
(3) Nimbus or rain clouds (Fig. 29) consist of thick masses of dark 



TYPES OF CLOUDS 



63 



clouds without definite shape and with ragged edges, from which 
continued rain or snow generally falls. Nimbus clouds are rarely 
more than half a mile above the earth's surface. (4) Cirrus clouds 
are delicate, fibrous, or feathery (Fig. 30). They are generally white, 




Fif 



Fig. 29. 




Fig. 28. 
Navy.) 

Fig. 29. 
of Navy.) 

Fig. 30- 

Fig. 31. 
of Navy.) 



Fig. 30. Fig. 31. 

Cumulus clouds. (Cloud chart, Hydrographic Office, Dept. of 

Cumulo-nimbus clouds. (Cloud Chart, Hydrographic Office, Dept. 

Cirrus clouds. (Cloud Chart, Hydrographic Office, Dept. of Navy.) 
Cirro-stratus clouds. (Cloud Chart, Hydrographic Office, Dept. 



and sometimes arranged in belts. They are usually high, five miles 
or more, and thin, and probably always consist of particles of snow or 
ice. Between these types of clouds there are many gradations, of 
which perhaps the most interesting is the cirro-stratus (Fig. 31), a 
thin, veil-like cloud, almost imperceptible, usually extending in a sheet 
over a large part of the sky. 



64 CLIMATIC FACTORS: MOISTURE 

In general, cirrus and cumulus clouds are fair-weather clouds, 
and do not give precipitation. The latter, however, may grow into 
the cumulo-nimbus or summer thunder cloud (Fig. 29), lose their 
fleecy whiteness, and produce rain. Cirro-stratus, stratus, and nim- 
bus clouds are more likely to be foul-weather clouds. 

Cloudiness and sunshine. The chief importance of clouds is 
found in their relation to (1) precipitation and (2) sunshine. Clouds 
cut off sunshine and reduce the amount of insolation; hence they 
lower day-time temperatures. Clouds also check radiation, and 
so tend to keep night temperatures higher. Cloudy regions, there- 
fore, have less variable temperatures than clear ones, Through their 
effect on temperatures, clouds also affect humidity and evaporation, 
raising humidity and lowering evaporation. Hence cloudy places 
are generally cool and damp and the types of vegetation and the 
crops grown there are different from those of places in the same 
latitude where clouds are few. Thus there are few vineyards in 
cloudy regions, wine production being typical of sunny countries. 

In general, great cloudiness goes with great relative humidity. 
Cloudiness is somewhat greater in winter than in summer, greater 
in higher latitudes than in low ones, and greater along sea-coasts 
than in continental interiors. The sunniest parts of the earth are hot 
deserts. 

Precipitation. The condensation of the water vapor of the air 
leads to rain, snow, or hail, if the products of condensation fall. 
Whether precipitation really takes place after the formation of clouds, 
depends on many conditions. To give rain or snow, the particles of 
water or snow in the cloud must be large enough to fall. Drops of 
rain vary in diameter from I /$o to V5 of an inch. If they are to reach 
the ground they must not pass through air which is dry enough and 
warm enough to evaporate them before they reach the bottom of the 
atmosphere. In desert regions, water may sometimes be seen to be 
falling from a high cloud, when not a drop reaches the ground. The 
falling drops evaporate as they descend. 

Precipitation and evaporation. The distribution of rainfall 
depends, in large measure, on the winds, and will be considered later. 
The amount of rain necessary for crops is affected greatly by rela- 
tive humidity and evaporation. Thus two localities which have the 
same amount and seasonal distribution of rainfall may have very 
different sorts of plants, because more of the precipitation in one place 
is evaporated quickly. 



EVAPORATION AND PLANT LIFE 65 

In some parts of western Texas, with a precipitation of 22 inches, there is 
too little moisture for crops unless they are grown by "dry-farming" (p. 329), 
and the region is given over largely to grazing. In the valley of the Red River in 
Minnesota and North Dakota the precipitation is a little less; yet this is one of the 
most important wheat regions of the world. The difference between the two 
regions is due chiefly to the fact that evaporation is about 2}4 times as great in 
Texas as in the Red River Valley, because of the higher temperature in the former 
place. 

In many other localities where rainfall is scanty, evaporation is one of the 
most important of all climatic factors, so far as vegetation is concerned. Dry- 
farming depends partly on the principle that if evaporation from the soil is checked, 
even scanty rainfall (15 inches yearly) may suffice for hardy crops like wheat. 
The so-called "hot winds" which sometimes do great damage to the corn crop, as 
in Kansas and Nebraska, owe their destructiveness chiefly to the rapid evaporation 
caused by their warmth and dryness. If these winds were moist, their temperature 
would not hurt the corn. Desert plants have peculiar characteristics such as 
fleshy leaves and smooth, shining surfaces, developed apparently with reference to 
preventing loss of moisture by evaporation. 



Questions 

1. Why is the crop in a grain field poor around the base of a tree? 

2. Where, in middle latitudes, would you expect the sensible temperature to 
be highest in summer? In winter? The same for tropical regions. 

3. Why is the relative humidity in houses in winter different from that out of 
doors, even where the furnace has a supply pipe taking in outside air? 

4. What is the effect of the indoor relative humidity in winter on the amount 
of fuel burned? 

5. Beds of rock salt are found underground in some places. What con- 
clusion may be drawn as to the climate when the deposit was formed? 

6. Why does fog in the evening appear first close to the ground? 

7. Why are clouds rarely formed above an altitude of 10 miles? 

8. Why does most of the heavy precipitation come from low clouds? 

9. What is the reason for the formation of more dew on surfaces of stone or 
metal than on pieces of wood near by? 

10. Explain the fact that the lower leaves or branches of a plant may be 
nipped by frost, when the upper parts of the same plant are unaffected. 

n. Why is frost less likely to occur on cloudy than on clear nights? 

12. Why are frosts less common after heavy rain than at other times? 

13. Why does a covering of newspapers or of thin cloth often protect plants 
from frost? 

14. Suggest other means by which protection from frost might be secured for 
large fruit orchards and truck farms. 

15. At what time of day is relative humidity lowest, on the average? Why? 



CHAPTER VII 
CLIMATIC FACTORS: PRESSURE AND WIND 

Pressure 

Importance of pressure. The downward pressure (or weight) 
of the air is about 15 pounds to the square inch at sea-level. The 
pressure varies a little from time to time at any given place, and is 
rarely the same at any two places more than a 
few miles apart. In themselves, variations of 
pressure have little effect on life; but the vari- 
ations have much to do with winds and other 
elements of weather, and weather is most impor- 
tant to life. Hence it is desirable to have some 
simple method of measuring and recording at- 
mospheric pressures. The instrument by which 
they are measured is the barometer. 

The barometer. The principle of the barometer is as 
follows: A tube more than 30 inches long, closed at one 
end, is filled with mercury. The open end of the tube is 
then placed in a dish of mercury (Fig. 32). The mercury 
in the tube will sink until its upper surface reaches a level 
about 30 inches above the level of the mercury in the 
dish, if the place of the experiment is at sea-level. The 
mercury remains at this height in the tube, because the 
pressure of the air on the mercury in the dish is enough to 
balance the weight of the mercury in the tube. Since the 
normal pressure of the air at sea-level balances a column 
of mercury about 30 inches high, the pressure of the air at 
sea-level is said to be 30 inches. If the pressure is more 
than 30 inches it is said to be high; if less than 30 inches, 
low. At sea-level the variation above and below 30 inches 
is rarely more than one inch. 



Fig. 32. Diagram 
to illustrate the prin- 
ciple of the barom- 
eter. The pressure 
of the air at A main- 
tains the mercury at 
B in the tube when 
there is no air in the 
tube above B. 

normal pressure 
about 24 inches 



Pressure and altitude. At elevations above 

sea-level the pressure grows less. Thus the 

is about 28 inches i,Soo feet above sea-level, 

at 6,000 feet, and about 20 inches at 10,500 feet. 

66 



WHY AIR PRESSURE VARIES ' 67 

The rate of decrease of pressure with increasing height being 
known, the altitude of a place above sea-level may be measured by 
means of the barometer. A special form of barometer has been de- 
vised for this purpose. 

The decrease of pressure with altitude explains some of the discomforts, 
such as mountain sickness, experienced by many mountain climbers. After a 
short stay at relatively high altitudes, these discomforts disappear in most 
cases. 

Distribution of pressure. The pressure of the atmosphere at 
sea-level varies from point to point, and from time to time at the 
same point. Some of the reasons are: (1) The temperature of the 
surface on which the air rests is unequal, and increase of temperature 
makes the air lighter. As the temperature varies, the pressure varies. 
(2) Water vapor in the air makes the air lighter (p. 56). The amount 
of moisture in the air is greater in warm regions (but not in hot des- 
erts) than in cold ones, and greater over moist surfaces than over dry 
ones. Since the amount of moisture in the air varies from time to 
time, the pressure is changing constantly. 

Representation of Pressure on Maps and Charts 
Isobars. For convenience in the study of pressure distribution, 
lines may be drawn on maps connecting points where the atmospheric 
pressure is the same. Such equal-pressure lines are isobars. A 
map showing lines of equal pressure is known as an isobaric map or 
chart. An isobaric chart for the year shows isobars connecting points 
having the same average pressure throughout the year. There may 
be isobaric charts for a season, for a month, or for shorter periods. 
The daily weather maps are daily isobaric charts. Fig. 33 is an 
isobaric chart for the year. The figures on the lines indicate the 
average pressure for the year in inches. 

In the southern hemisphere, the isobar of 30 inches encloses a 
belt extending almost around the earth, being interrupted only near 
Australia. Every point within the area enclosed by this isobar has 
an average atmospheric pressure of more than 30 inches. Every 
point within the isobar of 30.10 inches has an average annual pressure 
of more than 30.10 inches, while every point between the isobars of 
30 and 30.10 has an average annual pressure of more than 30 and 
less than 30.10 inches, etc. Between the two adjacent isobars of 
29.90 in the equatorial part of the Atlantic, the pressure is, on 
the average, less than 29.90, but not so low as 29.80. If the 



68 CLIMATIC FACTORS: PRESSURE AND WIND 




RELATIONS OF TEMPERATURE AND PRESSURE 69 

pressure sank to the latter figure, there would have been an isobar 
of 29.80 inches. 

It will be remembered that in the case of the isothermal chart 
allowance is made for altitude above sea-level. In the same way, 
the pressures shown on land on an isobaric chart are those which 
would exist if there were no elevations above sea-level. For low 
altitudes the pressure decreases about . 1 inch for each 90 feet of rise. 

Courses of isobars. Returning to Fig. 33, several points are 
seen readily: (1) The isobars have a general east-west course, 
though many of them are not straight; (2) on the average, they show 
greater pressure in low latitudes than in high latitudes; (3) they are 
highest (that is, they show highest pressures) in the latitudes just out- 
side the tropics ; (4) they are more regular in the southern hemisphere 
than in the northern; and (5) they are, on the whole, more regular 
on the sea than on the land. 

The isobaric map for January (Fig. 34) shows also that-a~high- 
pressure belt is very wide in the northern hemisphere, especially on 
the land, which at this season (winter) is cooler than the sea. This 
fact suggests that high pressure goes with low temperature. In the 
southern hemisphere, January is a summer month, and the land is 
warmer than the sea. If high temperature causes low pressure, the 
pressure in the southern hemisphere at this time should be less than 
that in the northern, and it should be lower on the land than on the 
sea. The map shows that both these things are true. This chart, 
therefore, seems to show that high temperature reduces pressure. 

A study of the isobaric chart for July (Fig. 35) leads to the same 
conclusion. At that time of year, the pressure in the southern hemi- 
sphere (winter) should be higher, on the average, than in January 
(Fig. 34) ; especially should it be higher on land, as the map shows it 
to be. In the northern hemisphere in July, on the other hand, the 
pressure should be less than it was in January, and especially should 
it be less on land, which is much warmer than it was in winter. Fig. 
35 shows both these things to be true. We have confidence, there- 
fore, in the conclusion that high temperature reduces the pressure, 
while low temperature increases it. The charts furnish other evi- 
dences in support of the same conclusions. 

If temperature alone controlled pressures, they should be lowest 
near the equator, where it is warmest, and highest near the poles, where 
it is coldest. Fig. 33 shows that the average annual pressures are 
distributed in apparent disregard of temperature, for the pressures 



7o CLIMATIC FACTORS: PRESSURE AND WIND 




ISOBARIC CHARTS 



7i 




bO 



72 CLIMATIC FACTORS: PRESSURE AND WIND 

are highest neither where it is coldest nor where it is warmest. It 
is clear, therefore, that neither temperature nor latitude entirely 
controls the distribution of pressure. 

Isobars and humidity. We have seen (p. 56) that water 
vapor makes the air lighter. But the isobars are not lowest over the 
oceans in warm latitudes, where the air contains, on the average, most 
moisture. We conclude, therefore, that the amount of moisture in 
the air is not the chief factor controlling the isobars. 

Inequalities of temperature and moisture in the air are the only 
factors thus far studied which might affect the isobars; and since 
they do not explain the most striking feature in the distribution of 
atmospheric pressure, namely, the high pressures in relatively low 
latitudes, we conclude that something besides temperature and mois- 
ture must be involved in their explanation. The explanation of the 
high pressures just outside the tropics is not found on the isobaric 
charts, and will not be discussed here. 



Winds 

Importance. Horizontal movements of air are winds. Winds 
are important in many ways, as in carrying away the impurities of 
city air, in transporting dust and sand (p. 201), in furnishing power 
for windmills and sailing vessels, in increasing evaporation (p. 58), 
and in distributing the moisture of the air (p. 76) . Winds also affect 
human beings directly, for they lower the sensible temperature, and 
are, as a rule, invigorating, while calm air (if warm) is enervating. 

Winds are produced by unequal pressures at the same level. 
These inequalities are being renewed all the time by unequal heating, 
and in other ways ; hence winds always are blowing. 

Relation of winds to the distribution of insolation. If the 
air over the whole earth were quiet at a uniform low temperature, 
and if it could then be heated by the sun for a time without any 
horizontal movement, the effect would be to raise its surface every- 
where, and to raise it most where it was heated most, that is, in low 
latitudes (Fig. 36). Under these conditions there would be a baro- 
metric slope from low latitudes toward high latitudes. Before 
horizontal movement began, there would be no change of pressure 
at the bottom of the air, for the same amount (mass) of air would 
lie over each place, as before the heating. But if the surface of 
the air had the form shown by the dotted line in Fig. 36, the upper 



WHY WINDS BLOW 73 

air would move as shown by the arrows. Since the air in low lati- 
tudes is always warmer than that in high latitudes, the upper air 
should always be moving from the equatorial zone toward the polar 
zones in both hemispheres. These poleward movements of the 
upper air lessen the pressure at the bottom of the atmosphere in 
low latitudes, because air has moved away from them. After air 
has moved from the equatorial region toward the poles (Fig. 36), there 
is more air over a given spot in high latitudes than in low. A baro- 
metric slope is thus established toward the equator at the bottom of 
the atmosphere. Air then moves from higher latitudes to lower 
latitudes at the bottom of the air (Fig. 37). Here, then, we have the 



90° 0° 90° 

Fig. 36. The lower line may be taken to represent the surface of the earth; 
the upper solid line, the outer surface of the atmosphere as it would be if the 
temperature were everywhere equal. The dotted line shows the effect of heating 
on the surface of the air. Movement would result as indicated by the arrows. 



90° 0° 90 

Fig. 37. The movement of air indicated in Fig. 36 would result in further 
movement as shown by the lower arrows in this figure. 

elements of a general circulation, a poleward movement in the upper 
air, and an equatorward movement in the lower air. The unequal 
heating which generates these movements is in operation all the time. 
Effect of the extra-tropical belts of high pressure. From the 
belts of high pressure just outside the tropics the air flows to areas of 
lower pressure on either side, at the bottom of the atmosphere, giving 
rise to distinct wind zones. If the earth did not rotate, these move- 
ments of air would tend to follow meridians. Rotation, however, 
turns the air currents to the right in the northern hemisphere, and 
to the left in the southern. It follows that the winds blowing 
poleward from the high-pressure belts are turned toward the east 
in both hemispheres, and so become westerly winds (southwesterly 
in the northern hemisphere, and northwesterly in the southern; 



74 



CLIMATIC FACTORS: PRESSURE AND WIND 




Fig. 38). The winds blowing from the belts of high pressure 
toward the equator become easterly winds (northeasterly in the 
northern hemisphere, and southeasterly in the southern), and are 
known as trade-winds (Fig. 38). The zone along the equator, where 
the northeasterly and southeasterly trades meet, and where rising 
currents of air are stronger than horizontal movements, is known as 

the zone of equatorial calms, or 
"doldrums." The position of 
this zone of calms shifts a little 
with the sun. 

The westerly winds of mid- 
dle latitudes and the trades of 
low latitudes are the prevailing 
winds (planetary winds) at the 
bottom of the atmosphere. 

Periodic Winds 



When air is heated it ex- 
pands, and a given volume of 
it becomes lighter. This results 
in movements of convection 
(Fig. 37). One of the move- 
ments involved in convection is 
horizontal, and horizontal movement of the air is wind. On a cold 
day in winter, with a brisk open fire, cold air may be felt moving 
along the floor toward the fire. Such movement is analogous to wind. 
Unequal heating of the air is, therefore, a cause of air movements, and 
since the air is being unequally heated all the time, unequal heating is 
a cause of constant atmospheric movements. Some of the movements 
are horizontal, and some vertical; some are in the lower part of the 
air, and some in the upper. 

The unequal heating of the air is the immediate cause of certain 
familiar winds and breezes which blow at more or less regular periods 
and also interfere with the circulation indicated in Fig. 38. 

Land- and sea-breezes. On a sunny summer day, the land be- 
comes warmer than a nearby lake or sea (p. 40). The result is that 
the air over the land is warmed and expanded more than that over 
the sea, and air moves in from the water to the land, at the bottom of 
the atmosphere. This is the sea-breeze or lake-breeze. At night the 
land cools more than the water, and the air blows from the land to 



Fig. 38. Generalized diagram of 
wind directions at the bottom of the 
atmosphere. 






SEA-BREEZES AND MONSOONS 75 

the water, giving the land-breeze. The sea-breeze is strongest during 
the summer, and in warm regions. In many places it is felt inland 
20 to 30 miles. It lowers the temperature over the land to which it 
blows, and makes the conditions of life on many tropical coasts much 
more agreeable than they would be otherwise. It is partly because 
of the cool, refreshing sea-breeze that many people go to the sea-shore 
during the hot months. The effects of the sea-breeze are so bene- 
ficial in many places in the tropics that the natives of those regions 
call the sea-breeze the "doctor." Along certain coasts, fishermen 
put to sea in the early morning with the land-breeze, and return 
toward night with the sea-breeze. 

Monsoons. Some lands near the sea become so warm in summer 
that sea (from-sea) winds blow throughout the hot season, while land 
(from-land) winds hold sway during the winter. This is the case 
in India. Such winds, which change their directions with the sea- 
sons, are monsoon winds. 

Monsoon winds influenced greatly the development and conduct 
of trade on the Indian Ocean, sailing vessels timing their voyages so 
as to take advantage of them. The monsoon winds of India have 
much to do with bringing moisture from the ocean, thus influ- 
encing the rainfall upon which the crops to feed 250,000,000 people 
depend. 

Monsoon winds, or winds very much like them, are not confined to 
India. Winds blow from sea to land in summer and from land to sea 
in winter on the east coast of Asia. Spain affords another excellent 
example of seasonal winds. 

Besides the winds mentioned above, whose times of blowing are 
more or less regular, there are winds which blow at irregular times, 
and whose coming cannot be foretold long in advance. These irregu- 
lar winds are the chief cause of the uncertain elements of the weather. 
They will be considered in the next chapter. 

Wind velocities. Wind velocities are expressed usually in miles 
per hour; thus the trade- winds are said to blow from 10 to 30 miles an 
hour. The United States Weather Bureau also uses descriptive terms 
(as light, fresh, brisk) for a regular scale of wind velocities. A wind 
velocity of 60 miles per hour causes a wind pressure of nearly 10 
pounds per square foot at sea-level, while at 90 miles an hour this 
pressure is doubled. Hence the destructive violence of winds of high 
velocity. The greatest velocities, rising to 100 or more miles per 
hour, always are associated with irregular winds. 



76 CLIMATIC FACTORS: PRESSURE AND WIND 

The average velocity of winds is greater over the sea than over the land, 
because moving air is checked on land by friction with the uneven surface. It is 
greater in the upper air than in the lower, for the same reason. But the force of 
the wind at high altitudes is less than for the same velocities at sea-level, owing 
to the less density of the air above. 

Winds and Rainfall 
Importance of rainfall. Perhaps the greatest service of the 
wind is in carrying moisture from the places where it is evaporated 
to the places where it is precipitated. Rainfall is of great importance 
to all plants and animals which live on the land. Human activities, 
too, are much affected by rainfall, for no arid region supports a dense 
population, and no agricultural country, aside from small irrigated 
areas, can be prosperous if the rainfall is unreliable. 

Less than one-thirtieth of the people of the United States live in the third of 
the country where the rainfall is less than 20 inches per year. Soil is not productive 
unless adequately watered, even though it be rich in the elements necessary for 
plant food. 

Twenty inches of rain per year usually is considered to be the 
minimum for general agricultural purposes, but something depends 
on (1) temperature, (2) the soil, and very much on (3) the time of 
year when the rain falls and (4) the rate of evaporation, as determined 
by temperature, soil, and wind (pp. 59, 65) . The warmer and drier 
the climate, the more the water needed for crops. A very porous 
soil loses its moisture more quickly than a more compact one, and 
so needs more rain for crops. The total amount of rain necessary for 
agriculture is less if it falls when the growing crops need it most. 

Rain and snow are important not only as a source of water for soil, but as a 
source of supply for streams and wells. A mantle of snow also prevents great 
changes in the temperature of the soil beneath, and in this way protects many 
plants. So important is this effect that in some regions a heavy snow generally 
means good yields of fall-sown crops the next year. Snow hampers some kinds 
of transportation and favors others. In lumbering, for example, snow makes 
the hauling of logs easier. Rapidly melting snow and heavy rainfall on frozen 
ground cause destructive floods. Heavy rain in a city is beneficial in flushing 
and cleaning the streets and in washing impurities out of the air. On the other 
hand, it may flood cellars and basements, doing great damage. Both rain and snow 
hinder the circulation of dust and bacteria, thus further contributing to health. 

The precipitation of any given region depends largely on (1) what 
winds affect it, (2) the topography of the surface over which the 
winds blow before reaching it, and (3) the topographic situation and 
relations of the place itself. 



WINDS DISTRIBUTE RAIN 77 

Rainfall in the zones of the trade-winds. In the trade- wind zones, 
the winds blow from higher to lower latitudes, and therefore, on the 
average, from cooler to warmer places. As the air is warmed, it 
can hold more moisture. So long as the trades blow over the sea or 
low land, they take moisture, but do not drop what they have. It 
follows that on the sea, and on comparatively low lands, like the 
Sahara and parts of Australia, the trade-winds are "dry." If, how- 
ever, the air of the trades is forced up over mountains, it is cooled, 
and some of its moisture may be precipitated. The windward sides of 
high mountains in the trade-wind zone have heavy rainfall. An illustra- 
tion is afforded by the east side of the Andes Mountains in the trade- 
wind zone (Fig. 39) . Even in the midst of the Sahara and of Australia, 
some rainfall is caused by high hills and mountains which stand in 
the path of the trade-winds. 

After the air of the trades passes over a mountain range, it de- 
scends and is warmed both by contact with the warm surface and 
by compression. It accordingly takes up moisture. The leeward sides 
of mountains in the trade-wind zones are therefore regions of little pre- 
cipitation. The west slope of the Andes Mountains in the zone of 
the trades furnishes an example in the coastal desert of Peru. 

Rainfall in the zones of the prevailing westerlies. The wester- 
ly winds are, on the whole, blowing from lower to higher latitudes, and 
so are being cooled gradually. They may, therefore, yield some 
moisture even at sea-level or on low land, and especially on land in the 
winter season. The heat of the land in summer often prevents 
condensation and precipitation of the moisture in the westerly winds 
until the air has moved far to poleward. But when such winds cross 
mountains, they yield moisture to the windward slopes and sum- 
mits, and become dry on the leeward slopes (Fig. 39). 

From these principles we may understand the rainfall of the 
United States, so far as it depends on planetary winds. The pre- 
vailing winds for most of the country are from the southwest. Com- 
ing to the land from the Pacific Ocean, these winds find the land 
cooler than the ocean in winter, and warmer in summer. In winter 
they yield moisture, even at low levels. This gives the low lands of 
California their wet season. As the winds blow across the mountains 
back from the coast, they yield more moisture, so that all the area 
west of the top of the first high ranges, the Sierras at the south and 
the Cascades at the north, is supplied with rain and snow in the 
winter season. As the winds blow beyond the Sierra Nevada and 



78 CLIMATIC FACTORS: PRESSURE AND WIND 




RAINFALL OF THE UNITED STATES 79 

Cascade mountains, the afr descends and becomes warmer, and 
therefore dry. East of these mountains lie the arid and semi-arid 
lands of the Great Basin and of eastern Oregon and Washington. 

When the westerly winds from the Pacific reach the higher parts 
of the Rocky Mountains, which are higher in many places than the 
mountains farther west, they again yield some moisture. But farther 
east, all the way to the Atlantic, these winds are dry, for they cross 
no more high mountains, and they do not generally go far enough north 
to reach a temperature as low as that of the mountains they have 
passed. For some distance east of the mountains the rainfall is slight ; 
but east of central Kansas and Nebraska the lands are well supplied 
with moisture (Fig. 59). It is therefore clear that something besides 
the westerly winds brings rainfall to this region. This agent is 
the irregular cyclonic wind, to be studied in the next chapter. 

The winds which blow from the Pacific to the continent in sum- 
mer have a different effect upon rainfall. At this season, they find 
a temperature on the coastal lowlands higher than their own. They 
are therefore "dry" in this region, and give to much of California its 
dry season. Blowing inland, these winds reach mountains so high 
that the temperature is low enough to cause condensation and pre- 
cipitation, even while the low lands to the west are dry. In Wash- 
ington, the mountains near the coast are high enough to cause pre- 
cipitation even in summer. In Alaska, where some of the mountains 
always are covered with snow, precipitation is heavy in summer, and 
at high altitudes much of it falls as snow. 

Monsoon winds may yield much moisture. In general, they 
blow toward warmer regions, and so should be dry ; but they may be 
forced up over high mountains, and precipitation follows. The 
heaviest rainfall on record, on the southern slopes of the Himalayas, 
is due to moonson winds. As in the case of the planetary winds, it is 
the windward sides of the mountains which receive the heavy precipi- 
tation from the monsoons. It is clear, therefore, that the windward 
sides of high mountains are places of heavy rainfall and snowfall. 

Variation in rainfall. Some places which were once moist are 
now dry, as shown, for example, by petrified forests in the desert of 
southwestern United States. It is believed that a similar change in 
the past has made large areas of central Asia, formerly inhabited, too 
dry to support more than the scantiest population. In most places, 
the rainfall of corresponding months or seasons is rarely the same 
from year to year. These temporary variations are important 



80 CLIMATIC FACTORS: PRESSURE AND WIND 

factors (i) in floods, which in some cases cause great damage to prop- 
erty and heavy loss of life (p. 237), and (2) in droughts, which fre- 
quently result in even greater loss through damage to crops, and in 
some countries, as India and China, through deaths from famine. 
Australia has more than once been crippled by long-continued, 
severe droughts. In the United States, with other conditions equal, 
the yield of corn depends directly on the amount of rain falling in 
June and July. When the amount is small, the crop is short. Other 
crops show similar close relations to rainfall. The importance of 
good crops to the prosperity of the country indicates that relative 
reliability of rainfall is a great national asset. 



Questions 

1. What effect do high altitudes have on the power of a steam engine? 

2. Explain fully the effects on men (1) of a brisk wind, and (2) of calm air, 
in summer, in Louisiana. The same for winter. 

3. Why are the westerly winds and trade-winds appropriately called planetary 
winds? 

4. On which side of Lake Michigan is the lake-breeze stronger in summer? 
Why? 

5. At what time of year would seasonal winds from Lake Michigan be most 
felt in Chicago? 

6. How much force is exerted on the side of a house 60 feet long by 25 feet 
high, when a wind is blowing 90 miles an hour? 

7. How do seasonal (ocean -continent) winds affect the temperature of the 
east coast of North America in summer? In winter? How do they affect the 
west coast at the two seasons? 

8. In general, are winds stronger in California in winter or summer? Why? 

9. Why are the most desirable residential quarters of many manufacturing 
centers in the United States located to the west and northwest of the city? 

10. In what portions of the world would power from the wind be most reliable? 
In what portions of the land areas? Why? Where is it most likely to be utilized 
by man? 



CHAPTER VIII 
STORMS AND WEATHER FORECASTING 

Weather Maps 

Temperature, wind, rainfall (or snowfall), and cloudiness are the 
important elements in the weather of any place for any given time. 
As these elements are combined in different ways from day to day, the 
weather varies. Weather changes are important in so many ways that 
it is desirable, if possible, to know about them before they come. Thus 
winds of great velocity are dangerous to shipping at sea, and vessels, 
if warned of their coming, may remain in port. A freezing temperature 
in spring or autumn may cause losses amounting to hundreds of thou- 
sands, or even millions of dollars; but if due warning is given, it is 
possible in some cases to protect the crops which would be injured. 
In these ways and many more, weather changes and weather forecast- 
ing affect everyday life. 

Since weather changes are associated directly with irregular winds 
(pp. 85, 90), and these in turn depend on pressure, it is evident that 
weather forecasting must depend largely on a study of pressure con- 
ditions. Changes of pressure from day to day have much more to do 
with weather changes than anything else has. 

Isobaric lines (p. 67) and isothermal lines (p. 45) may be put on 
the same map, which may show also where the sun is shining, where 
it is cloudy, where it is raining, snowing, etc. Such a map is a weather 
map, and may be made for any region, to show the weather at any 
given time. Thus Fig. 40 is a weather map of the United States for 
January 9, 191 1. Like all weather maps, it shows (1) isobars (full 
lines); (2) the direction of the winds (shown by arrows); (3) the 
degree of cloudiness; (4) areas of precipitation; and (5) isotherms 
(broken lines). 

Weather maps for the United States are made by the Weather 
Bureau, a branch of the Federal Department of Agriculture. They 
are prepared in the chief cities, where telegrams are received twice 
daily from numerous Weather Bureau stations in different parts of 

81 



82 



STORMS AND WEATHER FORECASTING 




INTERPRETATION OF WEATHER MAPS 



83 



the country, telling the pressure, temperature, direction and velocity 
of the wind, cloudiness, and rainfall at the station whence the tele- 
gram is sent. 

Explanation of the Map 

(1) Isobars. The isobars of the map (Fig. 40) show a range of 
pressure from 30.4 inches in the area centering in the Mississippi 
Valley, to 29.4 in Maine, and 29.2 in Washington. The pressure 
is more than 30 inches in the central part of the country, and less 
than 30 inches on both the Atlantic and Pacific coasts. 

The isobar of 30.4 in the central part of the United States is a 
closed line. The center of this high-pressure area is marked "high" 
(p. 66). West and east 
of the high the pressure 
decreases steadily toward 
the coasts, where there 
are centers of low pres- 
sure, marked "low" 
(p. 66). The minimum 
pressure in the low near 
the Pacific coast, 29.2, 
is less than in that over 
Maine, 29.4. Atmospheric 
pressures generally are 
unequal in different parts 
of the country. Hence 
most weather maps show 
both lows and highs, or at 
least one of each. 

(2) Winds. Wherever 
barometric pressures are 

unequal, winds are the result. The arrows on a weather map show 
the direction of the winds. On January 9, 191 1 (Fig. 40), winds 
were blowing away from the high and toward the lows. The move- 
ments of air out from an area of high pressure constitute an anticy- 
clone, and the movements in toward an area of low pressure con- 
stitute a cyclone. A cyclone is one type of storm. The winds in a 
cyclone are not always strong — rarely strong enough to be destruct- 
ive. The violent wind-storms which are popularly called cyclones 
should be called tornadoes. 




Fig. 41. Diagrams to show the circulation 
of air about a low, L, and a high, H, in the 
northern hemisphere (N) and the southern hemi- 
sphere (S) . 



8 4 ' 



STORMS AND WEATHER FORECASTING 



Winds do not blow straight out from the anticyclonic centers, nor 
straight in toward the cyclonic centers. They may start straight out 
from the center of each high, but in the northern hemisphere they are 
turned (deflected) toward the right (right-hand half of Fig. 41, N). 
Similarly, the winds which blow toward the cyclonic centers do not 
blow straight toward them, but are deflected a little to the right in the 
northern hemisphere (Fig. 40, and Fig. 41, N). In the southern 
hemisphere, the winds are turned to the left instead of to the right 
(Fig. 41, S). 

The weather map tells nothing directly about actual wind veloci- 
ties. This information appears in a table printed on the margin. 
But the strength of the winds at various points may be inferred from 
the map. In general, the winds are strong where isobars are 
crowded. 

As air moves in toward the center of a cyclone, it also moves 
spirally up (Fig. 42). The outflow above is chiefly to the eastward, 































>*; 






















yy 


f/% „ 


^r ^*- 


>* 
















yy y 


/ y . 


f ^ ' 




J ^~ 


^ — ^- 










__— —^ 


/ y 


/ / / 


/ s 


y . 


' * 


v y 










^_^^' 


y / 


/ / / 


/ 


/ / 


( 


( 












" y > 


' / / 


( 


' ( 


K 


L^ 














/ / 


\ 


v 








— 








— *"" ^ 


• / 


\ 


^- 










mtt- 






:rn- 


y 


X 








£aot. 





Fig. 42. Diagram illustrating the general movement of air currents in a 
cyclone of middle latitudes. The upper air moves mainly toward the east, in 
the direction of the prevailing winds. 

the direction toward which the prevailing winds of middle latitudes 
blow. This upward movement has an important effect on precipita- 
tion (p. 85). 

(3) Cloudiness and precipitation. An open circle on the shaft 
of an arrow (Fig. 40) indicates clear skies, a half-blackened circle (as 
in Wyoming) shows that the sky is partly cloudy, while a black circle 
(as in Montana) indicates general cloudiness. An R on the shaft 
of an arrow (as in California) indicates rain, and an 5 in the circle 
on the shaft of an arrow (as in New York) shows that snow is falling. 
Amounts of precipitation are given in the printed table with the other 
data for each station. 

(4) Temperature. As indicated above, the broken lines of a 
weather map are isotherms. The isotherms of Fig. 40, and of the 
weather maps which follow, show two distinct features: (1) they 



WEATHER OF CYCLONES AND ANTICYCLONES 85 

have little relation to parallels, and (2) all of them bend northward 
where the pressure is low, and southward where the pressure is high. 
These features are less pronounced on maps showing storms of less 
intensity. 

Cyclones and Anticyclones 

Characteristics of highs and lows. Highs and lows are some- 
times much more pronounced than those shown in Fig. 40. In 
the low of Fig. 43 the pressure ranges from 29 at the center, to 30.1 
in the East, and to 30.5 in the West. So great a range of pressure 
within the United States is uncommon. The isobars are closer 
together in this figure than in Fig. 40, and therefore indicate stronger 
winds. Cloudy skies prevail in the southeastern part of the cyclone. 

Highs as well as lows may have great area. Fig. 44 shows a high, 
or anticyclone, more than 2,000 miles across, with a great range of 
pressure. The isotherms of this chart, like those of the preceding, 
stand in very definite relations to the isobars. Denver, in the anti- 
cyclone, is about 30 colder than the southern part of Maine, which 
is 3 farther north, but on the western border of a cyclone. 

Near centers of low pressure, rain or snow falls in many cases, 
while around centers of high pressure there is, as a rule, no precipita- 
tion. The chief reason for rain or snow about a low is that the 
inflowing, rising air expands and is cooled (p. 60), and so gives up 
some of its moisture. In the northern hemisphere, southerly winds 
to the southeast of storm centers are, in general, blowing from warmer 
to cooler places, and this may result in rain or snow. The prevailing 
winds which control the outflow in the upper part of a cyclone (Fig. 
42) tend to carry the rainfall to the east of its center. 

The circulation of winds around cyclonic areas is the real factor 
in drawing moist air northward from the Gulf of Mexico, and in 
giving abundant rainfall east of the Mississippi River. 

In an anticyclone there is a descending spiral movement of air. 
The descending air comes from an altitude where the air is colder than 
that at the bottom of the atmosphere, and hence brings a low temper- 
ature. Winds from anticyclones generally bring clear weather, but 
cold air moving down and out from an anticyclone may mingle with 
warm air about it, so as to cause some of the moisture of the latter 
to condense, giving rise to clouds, or even to precipitation. 

Movements of cyclones and anticyclones. Highs and lows do 
not remain in the same place from day to day. This is shown by 



86 



STORMS AND WEATHER FORECASTING 




Fig. 43. Weather map for January 16, 1901, showing a very pronounced low. 




Fig. 44. Weather map for December 9, 1898, showing a high of great size. 



MOVEMENT OF STORMS 



87 



Figs. 45-47, which are the weather maps of three successive days. In 
these figures areas of precipitation are shown by shading. 

In Fig. 45 there is (1) a low along the Atlantic coast; (2) a high 
central over Iowa; (3) a feeble low north of Montana; and (4) a high 
in Oregon. The map of the succeeding day (Fig. 46) shows (1) that 
the low of the Atlantic coast has disappeared (moved to the east) ; 
(2) that the high of the interior has moved to West Virginia; (3) that 
the low which was north of Montana has moved to Dakota; while (4) 
the high of the Oregon coast remains about where it was. The map 
of the next day (Fig. 47) shows (1) that the high of the Virginias has 




Fig. 45. Weather map for September 24, 1903. .The shading on this and 
succeeding maps indicates areas of precipitation during the preceding 24 hours. 



moved on, but not so far as on the preceding day; (2) that the low 
which was over North Dakota is now north of Lake Superior; (3) 
that the high of Oregon has moved east to Idaho and Montana ; and 
(4) that a weak low has developed in Oklahoma. 

The rate of progress of a storm is not the same as the velocity of 
its winds. The velocity of the wind depends on the differences in pres- 
sure. A weak cyclone, that is, one in which differences of pressure are 
not great, gives rise to weak winds, even though the center of the 
storm moves rapidly. A strong cyclone, that is, one in which the 



88 STORMS AND WEATHER FORECASTING 




Fig. 46. Weather map for September 25, 1903. 




Fig. 47. Weather map for September 26, 1903. 



PATHS OF STORMS 



89 



differences of pressure are great, gives rise to strong winds, even 
though the cyclone itself may move forward slowly. 

The rate at which cyclones move varies with the season, the 
average being about 37 miles per hour in winter and 22 in summer. 
Storms may move at twice these rates, however, or at less than half 
their usual speed. 

The course of a cyclone may be shown on a single map, as in 
Fig. 40. The row of arrows shows that the low of Maine has moved 
from western Canada. The mean tracks of cyclones and anticyclones 




Fig. 48. Chart showing the mean tracks of cyclones (light lines) and anticy- 
clones (heavy lines), and their average daily movement (broken lines). 



for the United States are shown in Fig. 48. The broken lines on this 
map, marked 1 day, 2 days, 3 days, and 4 days, show the average 
daily progress of storms which come from the northwest. 

Some anticyclones enter the United States from the Pacific, while 
others start north and northwest of Montana, or, at any rate, are first 
reported from there. Cyclones start in various places. Many of 
them appear first near the places where anticyclones start, but others 
appear first in Colorado, the Great Basin, Texas, and elsewhere. 

The passage of a cyclone or anticyclone involves changes in the 
direction of the wind, and usually also changes of temperature, 



go STORMS AND WEATHER FORECASTING 

humidity, and cloudiness. Thus in Fig. 46 the wind at St. Paul is 
southeasterly, though this city is in the zone of westerly winds. The 
next day, after the storm center has moved forward to a position 
northeast of St. Paul (Fig. 47), the wind is northwesterly. An east 
wind is. often the first sign of an approaching cyclone; and since 
many cyclones bring rain, an east wind generally is taken as a sign 
of approaching rain throughout much of the United States. 

Cyclones are, on the whole, more frequent and better developed 
in winter than in summer. They do not affect the air to great heights. 
Even when the great whirl or eddy is 2,000 miles across, its height 
(depth) is rarely more than 4 or 5 miles. The origin of the cyclones 
and anticyclones of middle latitudes is not well understood. 

Winds and temperatures incidental to cyclones and anti- 
cyclones. During the passage of a cyclone, the air to the southeast 
of the storm center is drawn from warmer (lower) to cooler (higher) 
latitudes. In midsummer this often gives rise to a hot wave, though 
not all hot waves are associated closely with cyclones. Similar winds 
are known as the sirocco in the western Mediterranean region, and by 
other names elsewhere. In eastern United States, numerous sun- 
strokes and deaths from heat prostration accompany some hot waves 
in their progress across the country. 

Air to the northwest of a cyclone moves from cooler (higher) to 
warmer (lower) latitudes. In winter, this may give rise to cold 
waves. These cold winds are known as northers in the southern part 
of the United States, and sometimes as blizzards in the northern 
part, though this name usually implies heavy snowfall and high wind, 
as well as low temperature. 

When warm, moist air is forced up over mountains, it precipitates 
some of its moisture (p. 77). The precipitation sets free heat, so 
that the rising air is cooled much less than it would be otherwise. 
Beyond the crest of the mountains it descends, and is warmed in the 
process. It is warmed much more (often twice as much) in the 
descent than it was cooled in the ascent. It may, therefore, descend 
as a hot wind. Such winds are known as chinook winds in the United 
States, especially just east of the Rocky Mountains. 

The chinook winds temper the rigorous winters of certain parts of the north- 
western states and the Canadian provinces east of the mountains. They fre- 
quently evaporate a foot or more of snow in a few hours. For this reason they are 
sometimes called "snow eaters. 1 ' These winds make winter grazing possible over 
large areas which otherwise would he covered heavily with snow. Chinook win 



f 



DESTRUCTIVE TROPICAL STORMS 



9i 



sometimes develop with great suddenness. In some cases the temperature has 
been known to rise 8o° in six or eight hours under their influence. 

The chinook winds of summer are sometimes so hot and drying as to wither 
vegetation, and occasionally to destroy crops. 

Tropical cyclones. Cyclones sometimes start in tropical regions, 
and follow courses very different from those of the cyclones of middle 
latitudes. Most of the cyclones of this class which reach North 




Fig. 49. Course of West Indian storms for August-October, 1878-1900. 
The heavy line indicates the mean track. 



America originate in or near the West Indies, and they are most com- 
mon in late summer and early autumn. They follow a northwesterly 
course until the latitude of Florida is reached. Here they commonly 
turn to the northward, and later to the northeastward, following the 
Atlantic coast. The heavy line of Fig. 49 shows the average path of 
tropical cyclones {hurricanes) for a period of years. 

Tropical cyclones are stronger than those of intermediate latitudes; 
that is, the pressure at the center is lower and the winds are higher. 
Many of them do great damage along coasts, both to shipping and to 
low coastal lands. The great storm at Galveston in September, 



9 2 STORMS AND WEATHER FORECASTING 

1900, resulted in a loss of 6,000 lives, and damage to property esti- 
mated at more than $30,000,000. Much of the destruction was due 
to water driven by the high winds over the low island on which 
Galveston stands. An expensive sea-wall (Fig. 50) has since been 
built, and the level of the city raised, to prevent the recurrence of such 
a disaster. 

In September, 1906, a West Indian hurricane swept the Gulf coast of Florida 
and Alabama, and then passed inland, with damage to shipping and crops estimated 
at 15 to 25 millions of dollars. Islands which lie near cyclone tracks suffer severely. 
Porto Rico, for example, has been devastated five times within the last century. 
The storm of 1899 was probably the worst. Coffee, sugar-cane, and tobacco crops 
were destroyed almost completely, more than 3,300 lives were lost, and the property 




Fig. 50. A cross-section of the Galveston sea-wall, showing plan of construc- 
tion and relative dimensions. The right-hand side faces the sea. 

damage was estimated to be not less than $35,000,000. During this storm 23 
inches of rain fell in 24 hours. These tropical storms are so violent that sailing 
vessels once within the storm's grasp rarely escape. For this reason there has been 
much careful study of these storms. Sailing directions, giving instructions how to 
escape from them, are now a part of the equipment of every vessel frequenting the 
oceans where tropical cyclones occur. 

In the Atlantic, tropical cyclones occur north of the equator, 
though not south of it ; in the Pacific, they occur both north and south. 
They occur in the later part of the hot season, and are believed to 
originate in strong convection (p. 38) currents. Fortunately tropical 
cyclones are much less frequent than cyclones of middle latitudes. 



FORECASTING THE WEATHER 93 

Weather Forecasting 

Weather predictions. Weather predictions are based on the 
facts shown on weather maps. As a rule, official predictions are 
made only for the 36 or 48 hours immediately following the hour when 
the map is made. Take, for example, the map of the 25th of Septem- 
ber, 1903 (Fig. 46). Rain accompanies the cyclone which is central 
over Dakota. Since this storm has, for the last 24 hours, been moving 
a little south of east at the rate of about 40 miles an hour, it is fair to 
presume that it will move in this same general direction at a similar 
rate for the next 24 hours. If, in this time, it advances to the Lake 
Superior region, it probably will bring with it weather similar to that 
which it is now giving to the region where it occurs. Hence, on the 
25th, the prediction might be made that rain is to be expected in 
about 24 hours in the region around the head of Lake Superior. 

On the 26th the prediction might be made that the low which is 
central north of Lake Superior (Fig. 47) will move on to the Gulf of 
St. Lawrence by the succeeding day, and that increasing cloud- 
iness and rain will accompany it. Rain for the region about Lake 
Huron and the area east of it may, therefore, be predicted for 
the 27 th. 

Temperature changes as well as changes in cloudiness and precipi- 
tation may be predicted. Thus in Fig. 45 the isotherm of 50 bends 
southward notably in the high, central over Iowa. As the high moves 
east, it probably will carry the low temperature with it. Hence 
it is safe to predict that the temperature will fall in the area into 
which the anticyclone is to move. The map of the succeeding day 
(Fig. 46) shows that the temperature of western Virginia has fallen 
from about 6o° to about 40 along the path of the high, while areas 
much farther north are warmer. 

Fig. 46 also shows that North Dakota and Alberta have a tempera- 
ture of 50 , that is, a temperature io° warmer than that of western 
Virginia. It will be noted, too, that the relatively high temperature 
of Dakota, Montana, and Alberta goes with a low. As the cyclone 
moves eastward, the temperature along its path probably will rise. 
This is shown by the map of the next day (Fig. 47), which shows a 
temperature of about 50 north of Lake Superior. The same map 
shows how the isotherm of 40 bends to the southward in front of the 
high which is central over western Montana. As the high of Montana 
moves eastward, it will be likely to carry a low temperature with it. 



94 STORMS AND WEATHER FORECASTING 

From this map, therefore, it may be predicted that the temperature 
in Nebraska, Kansas, Iowa, and Missouri will be lower. 

The time when the rain which a storm may bring to any given 
place will fall is calculated from the rate at which the storm is moving. 
In the same way, the prediction of the time of arrival of a cold wave 
which an anticyclone may bring is based on the rate of progress of 
the anticyclone. This rate is known in advance by telegraphic re- 
ports. Predictions concerning the weather may be made more readily 
for the central and eastern parts of the United States than for the 
western part, for the storms have been under observation longer 
before they reach the central and eastern states. 

Failure of weather predictions. Weather predictions, even 
for short intervals, often fail. The reasons are many, among them 
the following: (i) Cyclones and anticyclones sometimes depart 
widely from the courses they commonly take. In such cases, the 
places the storm was expected to pass do not have the weather which 
was predicted for them. Thus a storm may be in line for St. 
Paul, to which it is expected to bring rain and a rising tem- 
perature; but instead of keeping its course, it may turn off to the 
northward, and the rain which was predicted for that city falls 
farther north. 

(2) Storms change their rate of advance, and so arrive earlier or 
later than predicted. (3) Storms sometimes appear and disappear 
without warning. (4) A storm sometimes changes its character, 
becoming weaker or stronger. It then does not bring to the places 
it passes the w r eather predicted for them. 

Value of weather forecasts. In spite of all mistakes, the 
warnings of storms, floods, cold waves, etc., sent out by the 
Weather Bureau, have been of great benefit. It has been esti- 
mated that property valued at $15,000,000 was saved in 1897 
by warnings of impending floods. In 1910 the estimated saving was 
$1,000,000. 

In September, 1903, vessels valued at $585,000 were held in ports temporarily; 
along the coast of Florida, by storm warnings. The loss of the Boston steamship 
City of Portland, with all on board, in the great storm of November 28, 1898, was 
due to a failure to heed storm warnings which kept all other craft in port. Warn- 
ings led to the protection of Si, 000.000 worth of fruit about Jacksonville, Florida, 
in 1901, with an estimated saving of half this amount. Other warnings of cold in 
1901 were estimated to have been the means of saving more then §3,000,000 worth 
of property. Shipments of perishable products, like most fruits, may be damaged 
badly if freezing temperatures are encountered unexpectedly in transit. Mer- 



THUNDER-STORMS 95 

chants handling such products are saved much trouble and inconvenience by infor- 
mation from the Weather Bureau concerning the temperatures for which their 
shipments must be prepared. 

The annual saving of property in these various ways exceeds, 
several times over, the total cost of the Weather Bureau. 



Local Storms 

Thunder-storms. Thunder-storms are frequent in the United 
States. They are most common in warm regions, and in warm 
seasons. Further, they are most common on days which are unusually 
warm, and during the warmer parts of these days; but there are 
occasional thunder-storms in the winter, and there are thunder- 
storms at night. 

The first indication of a thunder-storm is usually a large cumulo- 
nimbus cloud, which, in the zone of the westerly winds, generally 
appears in the west. It moves eastward, and as it reaches the place 
of the observer, there is usually a smart breeze, or thunder -squall, 
rushing out before it. Shortly after the squall the rain begins to fall. 
The rainfall may be heavy, and the drops large, but the downpour 
does not usually last more than an hour, and in many cases much less. 
A second thunder-storm sometimes follows close upon the first. 

Lightning is due to the discharge of electricity from one part of a cloud to 
another, from one cloud to another, or from the cloud to the ground. When light- 
ning discharges approach the ground, they seek exposed objects in some cases and 
cause loss of property, chiefly through fire, and occasional loss of life. The thunder 
following the lightning is due to vibrations in the air caused by the electrical dis- 
charge. It sometimes happens that lightning at a great distance lights the clouds 
over a region where the electric discharge itself cannot be seen. This lighting of 
the clouds is often called heat lightning, because it is more commonly seen in hot 
weather than at other times. The rainbows which accompany or follow many thun- 
der-storms are due to the effects of the drops of water in the atmosphere as the sun's 
rays pass through them. 

In middle latitudes, most thunder-storms occur during the passage of cyclones, 
though they do not accompany all cyclones. They are more common on the south 
sides of cyclones than elsewhere, and many of them occur at a considerable distance 
from the center of the main storm. In middle latitudes, most thunder-storms 
move from west to east, while in the zone of trade-winds they move from east to 
west. In both cases they move with the prevailing winds. Much of the precipita- 
tion from summer cyclones is connected with thunder-storms. Hence localities 
having most of their rain during the warm season depend largely on thunder-storms 
for moisture. Not infrequently violent thunder-storms give precipitation in the 
form of hail. 



96 



STORMS AND WEATHER FORECASTING 



Tornadoes. When a convection current is very strong, and has a 
very small diameter, the whirl becomes so intense in some cases as to 
cause great destruction. A whirling storm of this sort is a tornado. 
Tornadoes, like thunder-storms, are phenomena of hot weather. 
They are rather less abundant in the later part of the summer than in 
the earlier part. They are more likely to occur in a cyclone than in 
an anticyclone. Tornadoes are associated in most cases with hot 
days, and with the warmest part of the day. 

The atmospheric pressure in the center of a tornado is usually 
much lower than in the center of a cyclone. In a very strong tornado, 
the pressure at the center may be a fourth less than that of its sur- 
roundings. This is one reason why the tornado is so destructive. 
During its passage, the pressure may be reduced from the normal 
amount, 14.7 lbs. per square inch, to three-fourths of this, or to 11 lbs. 
per square inch. If such a tornado passes over a closed building in 
which the air pressure is 2,117 1 DS - P er square foot, the pressure on the 
outside becomes 1,584 lbs. The 
walls are therefore pushed out 
with a force of 533 lbs. per square 
foot, and unless they are very 
strong, they will fall, as if the 
building had exploded. In some 
cases only the weaker parts, 
such as windows, yield. 

Not only is the pressure at the 
center of the tornado very low, 
but the area of the low pressure 
is very small. While a cyclone 
may be 1,000 miles or more 
across, few tornadoes exceed 
1 ,000 feet in diameter at the sur- 
face of the land, and many are 
only a few yards wide. The re- 
sult is that the winds are violent. 
Estimated by the size and weight 
of the objects moved, their 
velocities have been thought to 




Fig. 51. Funnel-shaped cloud of a 
tornado, Solomon, Kas. (U. S. Weather 
Bureau.) 



hour. 



reach 400 or 500 miles per 
With this velocity, or even a velocity much less, trees are over- 
turned, buildings unroofed or blown down, and bridges hurled from 
their foundations. 



DESTRUCTION BY TORNADOES 97 

A tornado is often seen first as a funnel-shaped cloud (Fig. 51), 
the point of which may be far above the ground. As the funnel moves 
forward, its lower end may rise or fall. The cloud is due chiefly to 
the condensation of moisture in the sharp convection current, and the 
funnel shape is due to the expanding and spreading of the air as it 
rises. 

The tornado is, of all storms, the most destructive, but, in most 
cases, it has a very narrow track, and does not work destruction for 
a very great distance, rarely more than 15 to 30 miles. 

One of the most destructive, though not one of the most violent, tornadoes of 
recent times was that at St. Louis, May 27, 1896. It accompanied a thunder- 
storm in the southeastern part of a cyclone, central some distance northwest of the 
city. The destruction of property in and about St. Louis was estimated at about 
$13,000,000. 

A more violent tornado was that at Louisville on the 27th of March, 1890, 
just before nine o'clock in the evening. Many weak buildings were wrecked, 76 
persons were killed and about 200 injured in Louisville alone, and the loss of prop- 
erty was estimated at about $2,500,000. 



Questions 

1. Explain the apparent contradiction in the fact that northeast winds, in 
most areas of the United States, are part of a storm coming from the west. 

2. Show by a series of diagrams, in their proper order, the weather changes 
which would take place at a given station on three successive days under the 
following conditions: (1) On the first day the storm center (low) is approaching 
from the southwest; (2) on the second day at noon the center is 200 miles away, 
directly to the south; (3) on the third day it has moved on in the normal direction, 
and at the normal rate. Diameter of the low, 1,000 miles. 

Make similar diagrams for the same place for a storm following a track 200 
miles to the north of the station. 

3. Make rules for forecasting temperature when the weather map shows 
isotherms running (1) east and west, and far apart; (2) north and south, and close 
together. 

4. Indicate what truth, if any, there is in the following weather proverbs: 
(1) "Too cold to snow." (2) "A white frost is a sign of a fair day to follow." 
(3) "Rainbow in the morning, sailors take warning; rainbow at night, the sailors 
delight." 

5. Suggest other weather proverbs which you have heard, and show whether 
or not they have any basis of truth. 

6. Why are large dealers in grains, cotton, and tobacco interested in the daily 
weather map? 

7. Suggest some of the changes in the climate of the United States which 
would result (1) if the Rocky Mountains ran east and west, along the entire length 
of the Canadian boundary; (2) if the area of the Gulf of Mexico were land. 



CHAPTER IX 
TROPICAL CLIMATE 

Extent of tropical regions. The tropical zone, as usually defined, 
is limited by the tropic of Cancer on the north and the tropic of 
Capricorn on the south. Other definitions of this zone have been 
suggested, as (i) the zone where the trade- winds blow, and (2) the 
zone where the palm tree grows, the palm being taken as the type of 
tropical vegetation (Fig. 52). Defined by parallels, the tropical 
zone covers about two-fifths the area of the earth. 

About one- third of all the land — in round numbers, 17,000,000 
square miles — is within the tropics. This third of the land sup- 
ports about a third of the people of the earth — in round numbers, 
500,000,000. Much tropical land is desert, and much is covered 
with dense forests (Fig. 53), and these parts are but sparsely peopled; 
but the fertile areas which are cultivated support dense populations. 
In Java, for example, 30,000,000 people live in an area two-thirds 
that of Pennsylvania. About one-seventh of North America and 
one-sixth of its people are in the tropics. The tropical part of South 
America is much larger, nearly three-fourths of the continent and of its 
people being between the Caribbean Sea and the tropic of Capricorn. 
No part of Europe is in the tropics, and only about one-fifth of Asia is 
tropical, but this fifth supports fully half the population of the conti- 
nent. Three-fourths of Africa are in the tropical zone and two- thirds 
of its people, and about half of Australia and one-fourth of its people. 

The area of ocean within the tropics is about 70,000,000 square 
miles. The large proportion of water in this zone gives much of 
the land a marine climate. Relatively small areas, in the wider 
parts of the continents, show true continental conditions. 

General Characteristics of Tropical Climates 

The most striking thing about the climate of tropical regions 
is its uniformity. The weather does not change frequently, as in 
middle latitudes. Atmospheric conditions are so nearly uniform 

98 



TEMPERATURE CONDITIONS IN THE TROPICS 99 



month after month that weather and cli- 
mate are almost the same. Now and then 
hurricanes and typhoons occur in some 
parts of the zone. 

Uniformity of temperatures. The 
temperatures of the tropics are even more 
uniform than the other elements of cli- 
mate. (1) The noon altitude of the sun 
varies much less than in other zones, and 
(2) the length of day and of night is always 
nearly the same. As a result, the amount 
of insolation never varies much, and since 
it is always large, the temperature is 
always high, except at high altitudes. 

Annual changes. Many tropical 
places have a range of less than io° 
between the mean temperatures of the 
warmest and coldest months, and a range 
of less than 15 is characteristic of most 
tropical lands. On the oceans, and on 
some lands, the range is insignificant. At 
Bogota, Colombia, the coolest month is 
less than 3 cooler than the warmest. 
Buitenzorg, Java, has an annual range of 
only i.8°. Toward the edges of the 
tropical zone, the annual range of tem- 
perature is greater, especially inland. 
Thus at Nagpur, in the interior of India, 
Lat. 2i°9 / , the range is 27. i°. 

Diurnal changes. In many parts of 
the tropical zone, the difference in tem- 
perature between day and night is greater 
than that between the warmest and the 
coolest months. Near coasts, the tem- 
perature rarely falls below 70 at night, or 
rises above 90 by day. Inland, the range 
is much greater, and in dry regions far 
from coasts it is as much as 6o° or 70 in 
some places (from 50 or 6o° at night, to 
a maximum of 120 by day). In places, 



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freezing temperatures have been known at 
sea-level, as in deserts near the margins of 
the zone. Since the daily range is several 
times as great as the range between the 
warmest and coldest months, it is a common 
saying that " night is the winter of the 
tropics." The daily range is much the same 
day after day. 

On the whole, the highest temperatures 
of the tropics are no higher than those of 
middle latitudes. It is not so much the 
high temperature, as the continued high 
temperature, which distinguishes tropical 
climate. 

Effects of temperatures. Seasonal 
changes of temperature are so slight that 
they have little influence on life — animal 
or plant. The likeness of one day to 
another, and of one month to another, is 
probably a chief cause of the habit which 
tropical people have of putting off every- 
thing possible until " tomorrow." 

In some parts of the tropical zone, high 
temperatures are associated with high 
humidity. This means a high sensible tem- 
perature, which is uncomfortable and harm- 
ful in various ways. Sunstrokes and heat 
prostrations are especially common among 
white people. The high temperature and 
humidity are also unhealthful, and together 
constitute one of the greatest obstacles to 
the life of white men in this zone. The 
dampness and heat are enervating, as illus- 
trated by the general laziness of tropical 
natives (p. 337) — a trait which appears 
sooner or later in most white people who 
remain in this zone. 

One of the most important results of the 
high temperature of tropical regions is that 
it permits vegetation to grow throughout 



RAINFALL IN THE TROPICS 101 

the year, where rainfall is sufficient. Many trees bear buds, blossoms, 
and ripe fruit at the same time. 

Variability of rainfall. The variability of tropical rainfall is in 
contrast with the uniformity of the temperature. Some places are 
always dry, and others always rainy. In some places there is no 
rain for months at a time, and almost daily rains during the rest of the 
year. Some places have one rainy season each year, while others 
have two. This variability of rainfall is the controlling factor in the 
climate where the other leading element, temperature, is nearly con- 
stant. In general, the variations of rainfall are definite and regular. 

The distribution of rain in the tropics is influenced by (i) winds, 
and (2) topography. The winds (and calms) most important in deter- 
mining the distribution of rains are (a) the trade-winds, and (b) the 
equatorial calms (p. 74). The calm belt moves north and south 
after the sun (p. 14), and its movement affects the position and ex- 
tent of the trade- wind belts. The periodic character of rains in this 
zone depends, therefore, mainly on the apparent movement of the 
sun north and south of the equator. 

Seasons of rainfall. For most places within the limits of the 
migrating belt of calms, the rain comes when the sun is nearly over- 
head, or a little later. In the trade-wind zone, as elsewhere, rain 
is likely to fall from air forced up over high elevations (p. 77). 

The distribution of rainfall through the year gives a basis for the 
division of the year into seasons. Some places have two seasons, one 
rainy and one dry, while others have four seasons, two rainy and two 
dry. The lengths of these seasons vary much from place to place. 

Effects on life. Rainfall is here the chief factor controlling the 
distribution of life, and many of its relations. This is illustrated 
(1) by the rapidity with which vegetation springs up when rain begins 
after a long dry season; (2) by the fact that over millions of square 
miles the planting of crops depends on the coming of rain; and (3) 
by the further fact that even the nesting of many birds takes place 
only in the rainy season. 



Types of Climate within the Tropics 

Rainfall and its effects furnish a basis on which different types of 
tropical climate may be distinguished. There are four principal 
types: (1) The equatorial type, affecting a zone of io° to 15 on 
either side of the equator; (2) the trade-wind type, affecting belts be- 



io2 TROPICAL CLIMATE 

tween the equatorial zone and the tropics of Cancer and Capricorn; 
(3) the monsoon type, especially about lands near the sea; and (4) the 
modification of these types produced by high altitudes, giving what 
may be called mountain climate. 

1. Equatorial Climate 

Temperature. Temperature is least variable in the equatorial 
part of the tropical zone. The differences of temperature here 
depend chiefly on (1) nearness to the sea, especially nearness to that 
sea from which the wind blows to the land, and (2) altitude. The 
typical marine climate of this belt has almost no change of tempera- 
ture from month to month. Thus Batavia, the capital of Java, has a 
mean annual temperature of 7 8.8° F., and the coolest month is only 2 
cooler than the warmest. In the interior of central Africa, on the other 
hand, the mean annual temperature may be the same as that at Bata- 
via, but from the warmest to the coolest month the range is io° or 12 . 

The daily range of temperature is almost always greater than 
the annual range. Quito, Ecuador, Lat. o°i4' S., at an altitude of 
9,350 feet, has an annual range of less than i°; but throughout the 
year the temperature in early morning is about 47 , while at midday 
it is about 66°. On coasts and low islands in similar latitudes, the daily 
range is less, say from 90 to 75 . People living under the latter 
conditions are very sensitive to marked changes of temperature, and 
for them a temperature much below 70 may mean actual suffering. 
Frost on low lands near the sea is unknown. 

Rainfall. The rains come, for the most part, in daily showers. 
Even during the season of greatest rain, almost every day has a clear 
morning, and the rain comes from thunder-storms in the afternoon. 
In many places they come with marked regularity at a certain hour 
in the afternoon. 

The migration of the belt of calms involves the movement of the 
zone of daily thunder-storm rains. All places alternately in and out 
of the belt of calms have wet and dry seasons. Near the borders of 
the equatorial region there is one short wet season and one long dry 
one. In the central part of the region there are two wet and two dry 
seasons, but the latter are not so dry as those farther from the equator. 

The rainfall of places near the margin of the equatorial belt is 
illustrated by that at Cochabamba, Bolivia, 17 20' S., which has 
plentiful rain during its summer (December to February), and a nearly 
rainless season from the middle of March to the middle of November. 



EQUATORIAL CLIMATE AND LIFE 103 

North of the equator, in the latitude corresponding to that of 
Cochabamba, the rainy season begins in May or June, and continues 
until September or October. Since there is little difference in tem- 
perature between the various months of the year, the value of rain- 
fall for crops is about as great at one time as another. On the whole, 
rainfall near the equator is (1) more, and (2) less variable in amount, 
time of coming, and duration, than rainfall nearer the borders of the 
equatorial belt. As a rule, the farther a place in this belt is from 
the equator, the shorter its rainy season. 

Humidity and cloudiness. Humidity is high, as a rule, during 
the rainy season, and low during the dry season. While continued 
high humidity has bad effects on tropical people, as already pointed 
out, it favors heavy dews, which may be of great benefit where rainfall 
is scanty. Cloudiness is common during the rainy seasons, and 
where there are two rainy seasons, there may be cloudiness 70 or 80 
per cent of the time. 

The distribution of rain and clouds throughout the year affects 
the temperatures of the different months. As a rule, the end of the 
dry season has the highest temperature, and the rainy season is, in 
many places, the coolest part of the year, though the sun is then 
highest. This is due to the fact that the clouds shut off the sun's 
rays for a considerable part of the day. The increased humidity of 
the rainy season may make its sensible temperature higher than 
that of the hotter dry season. In many places, therefore, the rainy 
season is the most disagreeable time of year. Some tropical diseases 
are also most prevalent then. 

Moist equatorial climate and life. The high temperature of 
this zone and the abundant rainfall of its central portion favor a 
luxuriant growth of vegetation. Dense forests, such as those in the 
Amazon Valley, in central Africa, and in the Malay Peninsula, are 
characteristic of the humid parts of the zone. These forests are 
inhabited only by relatively sparse populations of backward natives, 
who live chiefly by hunting and fishing, and on the food supplied by 
the forest (pp. 337"339)- 

The moist equatorial climate is unhealthful, especially for white 
people. Tropical malaria, yellow fever, and intestinal disorders are 
the worst enemies which the white man meets near the equator. All 
these reach their maximum during the rainy season. The first two 
are spread by mosquitoes, and consequently are associated with wet, 
swampy places. 



104 TROPICAL CLIMATE 

Along the Amazon Valley, and especially on the equatorial coast of Africa, 
fevers almost control the location of residences for white settlers. If the white 
man escapes the fevers, there is still the climate itself with which he must contend. 
The never-varying high temperature, and the excessive moisture month after 
month, with never any stimulus from invigorating cold, gradually have their 
effect. Tropical anaemia appears sooner or later in most cases, and unless he seeks 
relief in a colder climate, the white man loses his physical and mental vigor. 

It is necessary to employ a force of men simply to keep the tracks of some trop- 
ical railroads clear of vegetation. Many wagon roads become impassable in the 
rainy season, and at these times a mud sledge, hauled by the water buffalo, is used 
in some regions, but it is a very primitive and unsatisfactory mode of conveyance. 
During the rainy season the rivers are swollen, and travel by boat is easier than at 
other times, for great sections of country are then flooded. 

Wooden railroad ties and telegraph poles decay rapidly, and it is necessary, in 
building railroads in parts of the tropics, to use special woods, which do not decay 
readily, or to substitute iron and concrete. The effect of all these things is to retard 
commerce. The most favored localities for trade in equatorial regions are those 
where a large river offers a natural trade route, and the river port is therefore the 
commercial center. Para and Manaos, on the Amazon, are examples of cities 
developed by river traffic through an equatorial forest. The commodities handled 
are largely forest products (p. 339). 

Dry equatorial climate and life. Toward the borders of the 
region of equatorial climate the absence or scantiness of rain through 
most of the year leads to vegetation very different from that nearer 
the equator. Grass lands replace dense forests (Fig. 53), the llanos 
of Venezuela, the canipos of Brazil, and the Sudan of Africa, being 
good examples. These regions are without large forests, since the 
period of growth, limited chiefly to the rainy season, is too short for 
trees. Scattered patches of forest, however, occur here and there, 
as in the campos of Brazil. 

The people of the grass lands are more advanced than the forest-dwellers nearer 
the equator. They get much of their living from flocks and herds. The necessity 
of moving frequently to find new pasturage for their cattle, goats, or camels, makes 
many of these pastoral people nomadic. 

In favored places, especially where irrigation is possible, the people become 
permanent settlers, and cultivate the soil. Outside the irrigated lands, crops are 
planted to some extent, but only in the rainy season, and only where the rainfall is 
considerable. Sometimes the rain fails to come at the expected time, or in the 
amounts expected. This uncertainty has retarded the development of agriculture, 
and has led to frequent famines. 

Irrigation may yet make productive much dry land in this cli- 
mate. Here white men may live with more comfort than nearer 
the equator, for the low humidity during much of the year is more 
healthful, and makes the high temperature easier to bear. The llanos 



CLIMATE OF TRADE-WIND BELTS 105 

of Venezuela, the campos of Brazil, and the African Sudan are there- 
fore, important regions with respect to future development. 

2. Trade-Wind Climate 

Winds and temperature. The most striking feature of the 
trade-wind climate is the steadiness of the winds, which blow with 
a velocity of 10 to 30 miles an hour throughout the year. The steady 
winds make the temperature conditions simple, especially over the 
oceans, and the climate of islands which lie in the trade-wind zone 
is about the simplest in the world. 

Both annual and diurnal changes of temperature are greater 
than in the equatorial belt. Low lands swept by the trades tend 
to be arid. They are warmed rapidly by day, and cooled rapidly 
at night, having in many places a daily range of 50 or 6o°. Tem- 
peratures as low as 32 are not unknown. These great changes are 
felt less than equal changes near the equator, because the humidity 
is low. The drier air with its greater changes of temperature makes 
the arid and desert lands more healthful than moist equatorial re- 
gions. In some ways the desert climate is invigorating, and diseases 
common in the equatorial regions are rare in many trade-wind dis- 
tricts. Man does not encounter the same kinds of difficulties, there- 
fore, as in the equatorial regions. 

Rainfall. Though commonly drying winds, the trades contain 
much water vapor, and become wet winds when cooled to the dew 
point. They are not so cooled over low lands, hence the latter are 
dry as long as the trades blow. Where they blow throughout the year, 
the land is desert (Fig. 39). On the other hand, where the trades 
blow over high lands, the ascending air is cooled, and clouds may 
form and rain fall. For this reason, the windward sides of highlands 
in the trade- wind belts are likely to be rainy, while the leeward sides 
are dry (Fig. 39). The leeward (westward) side of the Andes, from 
Ecuador to northern Chile, presents the strange spectacle of a coastal 
desert, and a similar condition is found on the leeward coast of south- 
west Africa. Highlands standing in mid-ocean also have a rainy side 
toward the trades, and a drier side in the lee, as illustrated by the 
Hawaiian Islands. 

In Australia (Fig. 54), a continuous highland lies close to the east coast, 
directly across the path of the southeast trades. The effect of this barrier is to 
increase the area of the interior desert, sometimes called the "dead heart of Aus- 
tralia," and greatly to restrict the spread of population (Fig. 55). 



io6 



TROPICAL CLIMATE 




Fig. 54- 



The importance of high lands in getting rain from trade-winds is seen in the 
fact that rain falls and vegetation nourishes (p. 334) on local elevations in the 
Sahara. Streams flow for short distances from the mountains, but soon dry up or 

are absorbed into the sands of 
the desert below. 

Most low lands affected 
by the trades are, on the 
whole, sunny, and trade- 
wind deserts are almost 
cloudless. This fact may 
have significance in the 
future, in the possible 
generation and storage of 
power derived from the 
heat of the sun's rays. 
Cloudiness is confined 
chiefly to windward 
slopes, which form but a 
small part of the total area 
of the trade-wind zone. 

The time of the rains 
in the trade-wind belts 
varies from place to place. 
In some places it is dis- 
tributed somewhat evenly 
throughout the year; in 
others it is seasonal. 
Places which get rain 
from the trade-winds 
have no rainless season 
if the winds are steady 
throughout the year, as 
in the central parts of the 
trade-wind zones. The 
trade- wind type of rain- 
fall is modified in latitudes low enough to be reached by the equatorial 
calms. Trade-winds are interrupted in some places by monsoon winds 
(P- 75)» an d where this is the case, they may modify rainfall conditions. 
Cyclones. The normal weather conditions of trade-wind belts 
are in places interrupted by tropical cyclones. They appear to origi- 







Fig. 55- 
54. Mean annual rainfall for Aus- 
(Diercke.) 

Fig. 55. Map showing density of popu- 
lation per square mile in Australia. (Lyde.) 



Fig. 
tralia. 



TRADE-WIND CLIMATE AND LIFE 107 

nate along the margins of the equatorial belt, and move to higher lati- 
tudes through the trade- wind zone (Fig. 49). They occur during late 
summer and early autumn only. They interfere with the regular daily 
changes of temperature, and in many cases they give torrential rains. 
Trade-winds and commerce. The steady, reliable trade-winds, 
which prevail over a wide east-west belt of the oceans, have long 
helped to determine the courses of sailing vessels, whose routes, going 
and coming, are different. 

Whaling vessels out-bound to the Pacific from New Bedford commonly went 
across the Atlantic to the Cape Verde or Canary Islands before turning south. 
Vessels in-bound from the Pacific to New England usually swing around Cape 
Horn, far out into the South Atlantic (Why?), and then sail directly home. 
The Panama Canal will be of little importance to sailing vessels going east, on ac- 
count of adverse winds. Similarly, the Red Sea presents head winds to sailing ves- 
sels going from the Indian Ocean to the Mediterranean. Unlike sailing vessels, 
steamers generally follow about the same course in both directions. 

Trade- wind climate and life. Temperature conditions are al- 
most as favorable for vegetation in the trade-wind zone as in the 
equatorial belt, but moisture is scanty. Forests as dense as those in 
equatorial climates occur on the windward slopes of some mountains. 
Most low lands in the zone of trades are arid. The Sahara, more 
than two-thirds the size of the United States, is an example. 

Considering the tropical zone as a whole, vegetation decreases 
in amount from the equator out (Fig. 53). This is illustrated well 
in Africa, which extends well beyond the tropics both north and 
south of the equator. Near the equator, there is the dense equa- 
torial forest, and on either side of it are belts of grasses, developed 
best in the Sudan. North of the Sudan is the Sahara, with little or 
no vegetation. South of the equator, in the area corresponding to 
the Sahara, the continent is narrower and the land higher, so that 
desert conditions are not as fully developed. 

Human life in the desert is controlled mainly by the climate 
(p. 332). Vegetation is so scanty that the people, depending for sup- 
port mainly on a few animals, must move frequently from one source 
of water to another. Deserts interfere in many ways with travel 
and communication among men, and a desert is almost as effective a 
barrier as an ocean to plants and animals (p. 331). Few beasts 
of burden can stand desert conditions, and caravan trade is carried 
on chiefly with the help of camels (p. 331). Food and useful materials 
of all kinds are scarce, yet the great daily changes of temperature 



io8 TROPICAL CLIMATE 

necessitate more clothing than is needed nearer the equator. White 
clothing is worn most, because it absorbs less sun-heat than dark 
fabrics. The clothing is loose, partly because such clothing is more 
comfortable in the heat, and partly because the danger of dust-storms 
makes it desirable to have a covering which can be drawn over the 
head quickly (p. 201). The people of deserts usually live in tents, 
or in loosely built, low, flat-roofed houses. There is no need for 
shutting out cold or rain, and when strong, the flat roofs are good 
places to sleep. 

Since fuel is scarce in the desert, cooking is of the most primitive 
sort. Much of the little meat used is air-dried. Utensils, such as 
vessels for holding water, are made of leather — about the only 
serviceable material to be had in many places. 

In parts of the deserts, showers occur now and then. In some 
places they come regularly at certain seasons of the year, and, in 
favored spots, the rainfall is enough to grow grain. In this case, 
the rainfall has a marked effect on the customs and religions of the 
people. In some places elaborate ceremonies are performed in honor 
of the rain gods before seeds are planted. The worship of rain, 
of rain clouds, or of the gods supposed to control them, is common. 
Sun worship is also common, for the sun is one of the most prominent 
things of the desert. 

3. Monsoon Climate 

Rainfall. At the season when the sun's altitude is greatest, 
the trade-winds are overcome, in some places, by the tropical mon- 
soon (p. 75). While the monsoon lasts, it may blow very steadily. 

Monsoons are well developed in southern and southeastern Asia, 
especially in India and thence to the China Sea. On the eastern 
coast of Asia, northward nearly to latitude 50 , there is a somewhat 
similar wind from the ocean in summer, which gives some rain to the 
land. For most places in the northern hemisphere, the monsoon 
season is between May and October. In the southern hemisphere, 
especially northern Australia, it is from November to April. The 
monsoon wind generally brings rain, and heavy rain on the windward 
sides of high mountains. A fall of 400 to 500 inches a year occurs in 
a few places. Since it all falls in four or five months, this means a 
daily rainfall of two to four inches throughout the rainy season. 

The Indian monsoon is a southwest wind, blowing from the Indian 
Ocean and the Bay of Bengal. Western and southwestern slopes 
therefore receive much rain, while the eastern coast, in the lee of the 



MONSOON RAINS 109 

Deccan plateau and Eastern Ghats, gets little rain while the monsoon 
blows. This coast gets its rain when the northeast trade-wind blows. 
In northwestern India there is a large desert, not reached by the mon- 
soon. Hence different parts of India have different types of rainfall, 
largely as a result of the relation of wind direction to topography. 

The conditions which produce rain mean increased cloudiness, 
and so the rainy season may be less hot than the others. As a rule, 
the highest temperatures occur just before the rainy season begins, 
for at this time the regular winds become weak or fail altogether. 
During the rainy season, the increased humidity more than offsets 
the comfort which the slightly lower temperatures might afford. 

Northern Australia (Fig. 54), and the northern coast of the Gulf 
of Guinea, in west Africa, have distinct tropical monsoon climates, 
but there are no important monsoon districts in the tropical lands of 
the western hemisphere, because the arrangement of land and water 
does not favor their development. 

Importance of monsoon rains. Monsoon lands afford rather 
easy conditions of life, so far as the needs of man are concerned, and 
they contain the larger part of the population of the tropical zone. 
India alone has 300,000,000 people, in an area less than two-thirds 
that of the United States. 

The importance of the monsoon rain to southern Asia can hardly be over- 
emphasized. During the dry season all vegetation withers, and the earth is 
parched and dusty. Hence the growing of crops and the support of the people 
over vast areas depend on the regular appearance of the rain-bringing monsoon. 
For one reason or another, the monsoons sometimes fail; still oftener they do not 
appear when they should, or stop sooner than usual; and finally, they are sometimes 
interrupted during what should be their proper season. The failure of the rain 
means loss of crops and famine for the dense populations of the monsoon districts. 
Famines usually leave hundreds of thousands of people in a weakened condition, 
so that ravages of epidemic diseases, like bubonic plague and Asiatic cholera, com- 
monly follow a famine. In India, deaths from famine and disease have exceeded a 
million in a single year. So great has been the loss of life, in some cases, that labor- 
ers enough to cultivate the farms were not left. The regions of famine are the 
regions of moderate rainfall (30 to 50 inches), where, in normal years, there is water 
enough for the crops. In other places, especially in southern China, too much rain 
sometimes brings disaster. Rivers rise high above their banks, destroying property 
and life; and famines resulting from the destruction of crops, at times cripple 
whole provinces. 

4. Climate in High Altitudes 
Effect on temperature. For most of the tropical zone, varying 
altitude is the one factor which causes important variations in tern- 



no TROPICAL CLIMATE 

perature. The extent of this variation is suggested by the fact that 
tropical mountains exceeding 16,000 feet are snow-capped. 

The lower temperatures found at moderate altitudes make pla- 
teaus in the tropics more agreeable and healthful than lowlands. On 
the Bolivian plateau, for example, the daily temperature may range 
from 3 2 to 75 or 8o°. White people living in the tropics seek the 
highlands, whenever possible, for residence (p. 320). The effect of 
the lesser heat even at altitudes of 7,000-8,000 feet is not, how- 
ever, equal to an invigorating cold season, like the winter of middle 
latitudes. The climate of tropical mountains and plateaus is some- 
what like the marine climate of the temperate zones. 

Vegetation and altitude. The vegetation, native and cultivated, 
of the higher altitudes of the tropical zone resembles that at lower 
levels outside the tropics. For example, on tropical highlands in 
Bolivia wheat and potatoes are common crops, whereas on most 
tropical lowlands they cannot be grown at all, or not as profitably as 
rice. There is a gradual change with increase of altitude, from 
products like sugar-cane or rice on the lowlands, through a belt 
of temperate-zone fruits or vegetables at a moderate altitude, to 
cold-temperate and Arctic types of plants, and then to perpetual 
snow at an elevation of about 16,000 feet. The snow and ice 
on the heights help to supply water for irrigation below. In 
places, too, the ice of the high mountains is carried down to 
settlements below. 

Population and altitude. An important effect of the highland 
temperatures is seen in the distribution of the population. From 
Mexico to Bolivia, most of the highlands are well populated, and the 
lowlands sparsely (Fig. 56). The single exception is Peru, where 
three-fourths of the people live on the coastal lowland, which is dry 
and healthful. Many of the chief cities are at elevations exceeding 
5,000 feet. 

In tropical America, it is common for the chief city to be on the 
highland in the interior, and for a smaller city, serving as a com- 
mercial outlet, to be on the hot, damp plain close to the sea. Mexico 
City and Vera Cruz, Caracas and La Guayra, Sao Paulo and Santos, 
are examples. Outside the cities, the highlands are the most thickly 
settled and the best developed sections, while the lowlands have few 
people, chiefly natives, and are but little developed. The result is 
that many of the chief products of tropical countries are not really 
tropical in character. 



LIFE ON TROPICAL HIGHLANDS 



in 



The decreased pressure of air which goes with increased altitude is of some 
importance in the higher tropical lands. As a rule the natives living at high alti- 
tudes (in Bolivia up to 15,000 feet) have a large lung capacity, on account of the 




Fig. 56. Map showing density of population per square mile in South Amer- 
ica. (Lyde.) 

thin air. They are active and well on the highlands, but usually sicken if taken to 
low lands to live. On the other hand, natives of lowlands experience discomfort at 
high elevations. The ill effects of lessened pressure are rarely felt below 5,000 feet. 



ii2 TROPICAL CLIMATE 



The Future of the Tropics 



Because of their more comfortable temperature and more health- 
ful conditions, the highlands of the tropics probably will be well 
developed earlier than the lowlands. At altitudes above 2,000 or 
3,000 feet, tropical diseases, particularly malaria and yellow fever, 
are not prevalent. Civilized peoples can live comfortably at these 
altitudes, and where they have not already done so, they are likely 
to establish themselves in lands of moderate height where there is 
adequate water, and from them direct the development of the adjoin- 
ing lowlands, the products and resources of which are of so much 
importance to the commercial world. 



Questions 

1. (1) If there were low land where the Gulf of Mexico and the Caribbean Sea 
are, what sort of climate would it have? (2) What effect would such a land area 
have on the climate of northern South America and Central America? 

2. Why are not the highest temperatures found at the equator? 

3. Explain the necessary relation of a place to the equatorial belt of calms, in 
order that it may have two rainy and two distinct dry seasons yearly. 

4. Why is there no desert in tropical South America east of the Andes? 

5. What changes would be produced in the climate of Australia if the main 
mountain range were on the west coast instead of near the east coast? 

6. Which of the two important tributaries of the Nile (Plate VI) is the first to 
be in flood each year? Why? Which has the greater flood? 

7. Suggest reasons which might delay the arrival of the Indian monsoon. 

8. Explain the distribution of rainfall in Australia (Fig. 54). 

9. What industries are likely to be connected with the distribution of popula- 
tion and rainfall shown in Figs. 54 and 55? 

10. Account for the distribution of population in Brazil (Fig. 56). 
n. Suggest ways in which the several types of climate found in the tropics 
might affect the character of imports from the outside world. 






CHAPTER X 

TYPES OF CLIMATE IN THE TEMPERATE (INTERMEDIATE) 

ZONES 

Extent of temperate zones. The two temperate (or inter- 
mediate) zones lie on either side of the tropical zone. Defined by 
latitude, their equatorial limits are the parallels 23^° N. and S. 
respectively, and their poleward limits the polar circles, 66>^° N. 
and S. There is, however, no marked change in climate as these 
boundary lines are crossed. The intermediate zones contain a 
little more than half (52.7 per cent) the area of the earth. 

Southern hemisphere. The total land area of the south tem- 
perate zone is only about 4,000,000 square miles (Fig. 57), and its 
population not more than 20,000,000. In other words, the lands of 
the south temperate zone, taken together, have an area about one- 
third larger than that of the United States, and a population less 
than one-fourth as great. 

About one-fourth of South America (1,800,000 square miles) 
and about the same proportion of its people (10,000,000) are south 
of the tropic of Capricorn. More than half of Australia and about 
three-fourths of its people (3,000,000) are in the same zone. Because 
of aridity this part of Australia is less important than the correspond- 
ing part of South America. New Zealand, but little more than 
100,000 square miles in area, has a population of about a million. 
About 7 per cent of Africa lies south of the tropic of Capricorn. 
This area (700,000 to 800,000 square miles) has hardly more than 
4 per cent of the people (5,000,000 to 6,000,000) of the continent. 

The area of ocean in the south temperate zone is about twelve 
times as great as that of the land (Fig. 57). Hence much of this 
zone has a marine climate, which is much less variable than the 
climates of the north temperate zone. 

Northern hemisphere. Nearly half of all land is in the north 
temperate zone, and the area of land there (26,000,000 square miles) 
is about equal to that of water (Fig. 58). In North America, all the 

113 



ii4 TYPES OF CLIMATE IN TEMPERATE ZONES 



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United States except northern Alaska, 
most of Canada, and part of Mexico, are 
in this zone. So also are nearly all of 
Europe, most of Asia, and part of northern 
Africa. This zone contains the greatest 
nations, and the majority of civilized peo- 
ple. Because of the greater expanse of 
land, continental climates are more pre- 
valent than in the southern hemisphere. 
Only in certain broad aspects can the 
climates of the northern and southern 
intermediate zones be discussed together. 



General Characteristics of Climates 
of the Temperate Zones 

Variability. There are several types 
of climate in these zones, and their differ- 
ences are perhaps as striking as their 
likenesses. Variability is the distinguish- 
ing feature of most of them. They vary 
in (i) temperature, (2) direction and veloc- 



£ ity of wind, and (3) amount and distribu- 
tion of rainfall. In general, the variability 
is less in the southern hemisphere than in 
the northern. 

Sun influence. The fundamental cause 
of variability in these zones, as contrasted 
with the uniformity of tropical climates, is 
the great variation in (1) the altitude of 
the sun during the year, and (2) the length 
of day and of night. The sun never is 
overhead at any place in these zones, and 
during at least a part of the year it is 
many degrees from the zenith at noon 
(pp. 13-14). There are, accordingly, great 
differences in the amount of heat received 
at different times, and the year is divided 
into seasons which vary much in temper- 
ature. 






3 o 

O 10 
X ._ 

U-, O 

ag 

5 ~ 

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TEMPERATURES OF INTERMEDIATE ZONES 115 



Winds. The prevailing (westerly) 
winds of these zones are much less regular 
in direction and velocity than the trade- 
winds of the tropical zone, and are inter- 
rupted much by cyclonic storms, which 
vary greatly in frequency and strength. 

Temperature ranges. The factors 
noted above lead to great variations of 
temperature from day to day, from season 
to season, and from place to place. The 
great and sudden variations of tempera- 
ture make the term temperate singularly 
inappropriate for these zones. The weather 
at least is often most intemperate. In 
contrast with the conditions in the tropical 
zone (p. 99), observations through many 
years are necessary to get a correct idea of 
the climate. The yearly range of temper- 
ature in most places is far greater than 
the daily range. 

In the same latitude, conditions vary 
widely from place to place, both with 
respect to variation of temperature and the 
time of greatest heat and cold. Inland, 
the highest and lowest temperatures of 
the year generally .occur about a month 
behind the highest and lowest noon-alti- 
tudes of the sun, and the temperatures of 
the warmest and coldest months may be 
50 apart, even in middle latitudes (as 
Chicago). Spring and autumn are much 
alike so far as temperature is concerned. 
Near the sea, the highest and lowest tem- 
peratures are about two months after the 
solstices, while spring is cold and autumn 
is warm. The maximum temperatures in 
summer in many cases exceed those of 
some tropical stations, and the lowest 
temperatures in winter approach polar 
cold. Summer weather is almost tropical, 



i 



l 



'"%. ■ \~H: 



&§ 



E S 



SJ 



n6 TYPES OF CLIMATE IN TEMPERATE ZONES 

and winter weather polar, in many parts of these zones. Weather 
and climate are therefore very unlike, so far as temperature is 
concerned. The average annual range, however, is as low as 20 
in some places, even in comparatively high latitudes. Hence, in this 
zone, latitude is not a sure index of climate. 

North temperate zone. The great expanses of land lead to 
marked contrasts in temperature between the two margins of this 
zone, within which some of the highest as well as some of the lowest 
known temperatures occur. The mean annual range varies from as 
little as 1 6° in southern California (San Diego, near the sea), to as 
much as 8i° in northwestern Canada (Fort Chippewyan, far from 
the sea to windward). 

Near the tropical margin of this zone, summers and winters are 
not extreme, and springs and autumns are long. Toward its pole- 
ward margin, on the other hand, the differences between summer 
and winter are great, and the transition seasons are short. Hence 
the length of the growing season for plants differs greatly in different 
parts of the zone, with important effects on life. 

The variations of temperature are accompanied by variations in 
rainfall. In tropical lowlands, where temperatures always are high, 
it makes little difference to vegetation when rain comes; but where 
there are seasons of radically different temperatures, rain is useful 
to plants in summer, but not in winter. There are two general types 
of seasonal rainfall in the temperate zones, the marine or winter 
type, and the continental or summer type. In general, windward coasts 
and islands have the former, while interiors and leeward coasts have 
the latter. 

Both the variations of temperature and the distribution of rain- 
fall have far-reaching effects on life, some of which may be pointed 
out. Civilization, which apparently began near the tropics, has 
moved steadily outward (especially northward), until its chief centers 
are now in the middle latitudes of the northern hemisphere (p. 114), 
where the seasons are commonly regarded as responsible for much 
of the energy, thrift, and industry which have brought about this 
advanced development. The change of seasons stimulates effort. 
In summer, the conditions of life in many parts of the temperate 
zones are almost as easy as in tropical regions. Summer is a time of 
abundance, and winter a time of scarcity, in nature's supplies. In 
summer, it is necessary to provide food, clothing, and shelter for the 
winter, when nature does not provide. In order to live, therefore, 



SUB-TROPICAL CLIMATE 117 

man must plan for the future, and to secure the things he needs 
requires regular effort; but with planning and effort, it is possible 
for him to secure what he needs. These conditions lead to mental, 
physical, and industrial development, and such development is the 
basis for advance in civilization. 

South temperate zone. The limited extent of land in the south 
temperate zone gives it a climate far less variable than that of the 
corresponding northern zone. 



Types of Climate 

The north temperate zone is a patch-work of climatic types, 
whether the division is based on temperature or on rainfall. The 
south temperate zone, with its smaller land areas, mostly near the 
sea, has few important types of climate. 

The chief types of climate of both hemispheres are determined 
by (1) the distribution of land and water, (2) winds, and (3) altitude. 
With insolation, these factors control both temperature and rainfall. 
The following important types of climate are recognized: (1) That 
of windward coasts in low latitudes, the sub-tropical type; (2) that of 
windward coasts in high latitudes (above 40 ) ; (3) that of continental 
interiors, a type which varies much, especially in amount of rainfall; 
and finally, (4) the modifications, particularly of (3), brought about 
by altitude. 

I. WINDWARD COASTS IN LOW (BELOW 40°) LATITUDES 

General characteristics. The chief features of sub-tropical 
climates are moderate temperatures, with small annual and large 
diurnal ranges. In these respects the climate resembles that of the 
tropics. The rainfall is rather light in most places (Fig. 39), and 
is greatest in winter. The summers are dry. This climate is typical- 
ly sunny, with a maximum of cloudiness in winter. 

Distribution. The sub-tropical type of climate is found in 
latitudes affected alternately by the trade-winds, the tropical belts 
of high pressure, and the westerly winds. It is developed best on 
islands and on the western (windward) coasts of continents between 
the parallels of about 25 and 40 . It prevails over much of the 
land of the south temperate zone and is widespread about the Mediter- 
ranean Sea, extending from Spain on the west through Italy and the 



n8 TYPES OF CLIMATE IN TEMPERATE ZONES 

southern part of the Balkan Peninsula into western Asia, as well as 
across the northern part of Africa. The wide extent of the sub- 
tropical climate about the Mediterranean has led to the name "Med- 
iterranean climate." In North America, this type of climate is 
almost confined to the coastal part of California, south of San Fran- 
cisco. The climate of southern California may be taken to illustrate 
the type. 

Southern California 

The southward migration of the wind systems in winter brings 
southern California under the influence of westerly winds. The 
northward migration of the wind systems in summer brings it in 
turn under the influence of (i) greatly weakened westerlies, (2) the 
tropical high pressure belt, and (3) the northern margin of the trade- 
winds. 

Temperatures. The latitude is high enough to prevent a long 
continuation of temperatures as high as those of the tropics, and 
nearness to the sea prevents the seasonal extremes characteristic 
of most places in the temperate zones. Freezing temperatures are 
rare in low altitudes. Daily ranges of temperature are greater than 
yearly ranges. On the whole, the temperature of southern California 
is much like that of tropical lands at moderate altitudes. 

In some ways the sub-tropical type of climate is the best in the 
world, and is described frequently as being like " perpetual spring." 
It is healthful, as shown by the popularity of southern California, 
where Pasadena, Riverside, San Diego, and other cities duplicate, 
on a small scale, the noted resorts in the Riviera of southern France 
and Italy. The sunny skies (68 per cent for San Diego) help greatly 
to make these places popular, especially in autumn, winter, and 
spring. The dry season (summer) may be disagreeable because of 
(1) the heat, (2) the drying up of vegetation, and (3) fogs and dust. 
Many places in California have least sunshine in the dry season on 
account of fogs. 

The absolute lowest temperature at San Diego is 32 , and the 
absolute maximum 101 . Such variations are characteristic of 
tropical lands where the average annual range is not more than 15 
to 20 . Interior stations show greater average ranges and more 
marked extremes, because they are farther from the sea. Their 
mean maxima are higher, their mean minima are lower, and the fre- 
quency of both high and low temperatures is much greater. 



MARINE CLIMATE 119 

Rainfall. As in most similar localities (Fig. 39) the precipita- 
tion in southern California is rather low, and there is a marked winter 
maximum. The summers are almost rainless for a period which 
varies considerably from place to place. The interior valley of 
California is dry at all times because the coast ranges have taken 
the moisture out of the winds from the ocean. The dryness increases 
the range of temperature in the valley. 

Rainfall and Crops 

During the dry season, most vegetation dries up unless irrigated. 
Where water is available, the abundance of sunshine and the favor- 
able temperatures lead to extensive irrigation, as in southern Califor- 
nia and in the favored parts of southern Europe, western Asia, and 
northern Africa. Most of the crops of these latitudes, however, are 
grown during the rainy winter season and harvested in spring, before, 
or soon after, the beginning of the dry season. Winter crops are 
made possible by the temperatures of that season. Winter wheat is 
a common cereal crop, as in Italy, southwestern Australia, and 
California, while barley, resistant to both heat and dryness, was 
long the chief cereal in such climates. Corn cannot be grown without 
irrigation, for it needs a high temperature (such as that of the dry 
season) during growth. 

The characteristic crop of the sub-tropical climate is fruit. 
Oranges, lemons, olives, grapes, and other fruits are produced 
abundantly in southern California and in Mediterranean lands. 
There is possibility of frost, however, and frost-fighting is an 
important part of the business of the California fruit grower. 
In many sub-tropical localities, fruit-drying is an important 
industry, favored by the dry, sunny weather which follows the 
ripening of the fruit. 



2. WINDWARD COASTS IN LATITUDES ABOVE 40°; MARINE CLIMATE 

Location. The marine type of climate in this zone is controlled 
by prevailing westerly winds, blowing almost constantly from ocean 
to land. The climate is cool, damp, and rainy. The change from 
the sub-tropical type of climate is gradual, and in some ways the 
two types are not very unlike. 

In the western hemisphere, this type of climate is developed best 
(1) in Chile, south of latitude 40 and west of the Andes Mountains, 



120 TYPES OF CLIMATE IN TEMPERATE ZONES 

and (2) near the coast from San Francisco to the Arctic Circle. It 
is modified greatly even east of the low coast ranges. 

In the eastern hemisphere, neither Africa nor Australia extends 
into latitudes high enough to have this type of climate; but it affects 
parts of Tasmania and most of New Zealand. It affects the coast 
of Europe from France to the Arctic Circle, and extends far inland 
because there is no continuous north and south mountain range to 
take the moisture from the westerly winds. The change from 
marine to continental conditions here is very gradual. From the 
British Isles, the annual rainfall decreases gradually eastward, the 
winter maximum gives way to spring and summer maxima, and 
the ranges and extremes of temperature become more marked. If 
the marine influence did not reach far inland, the densely populated 
and highly developed countries of western Europe, especially north 
of latitude 50 , would be far less important than now. The temper- 
ing effect of the westerly winds on the climate of western Europe is 
increased by the relatively high temperature of the central and 
eastern parts of the North Atlantic Ocean. 

Temperatures. The variations of temperature are less than 
in the same latitudes elsewhere. Thus the yearly range of tempera- 
ture at Sitka, Alaska, Lat. 57 , is only 25 , hardly more than that 
in some parts of the tropics, and at Thorshaven, in the Faroe Islands, 
Lat. 62°,the range is only 14. 2 . In this respect, this type of climate 
resembles the sub-tropical type, though the actual temperatures are 
lower (Why?). It is the only really temperate climate of the inter- 
mediate zone. 

Regions having a marine climate have mild winters and cool 
summers, and their average yearly temperatures are higher than 
those of other regions in the same latitude. For example, Ireland, 
which represents perhaps the extreme case, is 30 or 40 too warm 
for its latitude, 55 N. 

Rainfall and humidity. Places freely exposed to westerly winds 
get much rain in winter, when the land is cooler than the sea. In 
summer, low lands are warmer than the ocean and receive little 
rain, though the dry season is much shorter than in lower latitudes 
(Why?). Mountainous western coasts have abundant rainfall, high 
humidity, and much cloudiness all the year. In some places fogs 
occur almost daily, and in extreme cases, as along the coast of Alaska, 
they may last for weeks at a time. Evaporation is extremely low. 



MARINE CLIMATE AND LIFE 121 

Though the maximum precipitation is in winter, little of it is in the 
form of snow, except at high altitudes. 

Effect on life. Cool summers, abundant moisture, and much 
cloudiness, prohibit the growth of many kinds of crops. For example, 
wheat and corn are not grown in the typical marine climate of western 
North America and northwestern Europe. Wheat requires a dry, 
sunny harvest season, and so its growth near the coasts in question 
is confined to places where topography modifies marine conditions, 
as in eastern Washington and eastern England. Corn needs a higher 
temperature and more sunshine than the marine climate affords. 
Oats, rye, and barley, however, are grown successfully in a cool, 
cloudy, damp climate. This is a chief reason why oats have fur- 
nished the staple food of Scotland. Various crops are grown near 
the northern limit of the intermediate zone in northwestern Europe 
and in Alaska. In Norway, rye, oats, barley, and potatoes are 
grown successfully within the Arctic Circle. In Alaska, barley, 
potatoes, cabbages, and turnips have been grown at Ft. Yukon, in 
latitude 66° 30'. The marine climate is also favorable for grass, 
which in some places grows ten or eleven months in the year. 
For this reason, the raising of live stock is or may be important 
in this climate. In the British Isles, for example, the grazing in- 
dustry has long been the leading phase of agriculture. Mild tem- 
peratures and abundant moisture make Ireland always green (Emer- 
ald Isle), and the raising of cattle is a chief industry. 

Marine climate also favors the growth of heavy forests. Good 
examples of such forests are found in northwestern United States 
(p. 370), where lumbering is an important industry and forest prod- 
ucts are leading articles of trade. In the same region, mountains 
near the coast cause heavy precipitation, much of which is in the 
form of snow. The melting of the snow in summer keeps the streams 
full when the rainfall is least, and mountain streams afford water 
power (p. 290) for manufacturing. Among native tribes, forest 
conditions lead to hunting and fishing as regular pursuits. 

The change of climatic conditions with increasing latitude has resulted in 
striking contrasts in man's activities. In the northern part of Chile, for example, 
there is a coastal desert at the margin of the trade-wind zone. Here conditions 
have favored the accumulation of guano and nitrate deposits, which have been the 
basis of important industries and commerce, and the cause of bitter strife between 
Chile and Peru. South of the desert, the sub-tropical type of climate has led to 
irrigation and the growth of fruits. Still farther south, where the climate is of the 
type under consideration, grazing and the raising of cereal crops and vegetables 



122 TYPES OF CLIMATE IN TEMPERATE ZONES 

are the chief occupations. In the extreme southern part, the heavy rainfall from 
the westerly winds supports luxuriant forests, and forest industries and fishing are 
the chief occupations. Similar contrasts exist along the western coast of North 
America from California northward, and along the coast of Europe from Spain to 
Norway. 

3 CONTINENTAL CLIMATES 

Regions affected. This type of climate, as its name implies, 
is found inland from windward coasts; but not at any fixed distance 
from the coast. We have seen already that the marine climate 
extends far from the western coast of Europe (p. 120), and but a 
very short distance from the west coast of the Americas (p. 119). 

In the south temperate zone, the continental climate is found 
only in southern Argentina. North America and Eurasia, on the 
other hand, are broad in rather high latitudes (Fig. 58), and so have 
continental climates over wide areas. In North America, there is 
a sharp contrast between the marine climate of the western coast 
and the continental climate east of the westernmost high mountains, 
the continental climate affecting most of the United States and 
Canada. In Eurasia, because of conditions already noted (p. 120), 
the marine climate of western Europe grades into the continental 
climate which affects the Russian Empire and most of China. 

Temperatures. The chief characteristic of the continental 
climate is extremes of temperature. These extremes are due largely to 
the fact that land absorbs and radiates heat much more readily than 
water does. The winters are cold, the cold increasing (1) with the 
latitude, and (2) with increasing distance from the sea to windward. 
In latitude 45 , in North America, the lowest temperatures are 
about — 30 , and near the northern limit of the zone they reach — 6o° 
or even less. A great area in northeastern Asia, far from the ocean 
to windward, has extremely low temperatures in winter. In the 
United States, the temperature never falls to — 40 , except in the 
extreme northern part and in high mountains, and there but rarely; 
but, except in the Gulf region, there is no large area east of the 
Pacific coast where temperatures io° to 20 below freezing do not 
occur every year. The summers are hot. July averages of 6o° 
are found even beyond the northern margin of the zone, and maximum 
temperatures of 8o° to 90 are found close to the Arctic Circle. In 
the southern part of the zone, the summer temperatures are tropical. 

The annual ranges of temperature are very great, especially 
in the northern part of the north temperate zone. In northwestern 



CONTINENTAL CLIMATE 123 

Canada, the difference between the lowest and the highest tempera- 
tures of the year has been known to reach 150 , and in northeastern 
Asia, 180 . In the lower latitudes the extremes are not so great; 
the winters are milder, and the summers are not correspondingly 
warmer. In our southern states only small areas ever have tempera- 
tures above ioo°, and in most parts of the zone the mean maximum 
temperatures are under 90 , or no higher than those occasionally 
recorded near the Arctic Circle. 

Cyclonic influence. A second important feature of continental 
climate is the variability of weather from day to day. Cyclones 
and anticyclones interrupt the prevailing westerly winds frequently; 
hence there is repeated change from clear, cold, and dry days, to 
cloudy, warm, and damp ones. Because of the frequent storms, the 
winds may, in the course of a day or two, blow from all points of 
the compass, and each wind tends to bring its own distinctive weather 
conditions. The northerly winds of anticyclones in winter carry 
freezing temperatures almost to the southern margin of the zone. 
Southerly winds, on the other hand, carry warm air to comparatively 
high latitudes, and temporarily may produce a summer-like tem- 
perature in mid-winter, even as far north as New York and Chicago. 

Rainfall. A third important element of continental climate 
is its rainfall, which is very variable, but as a rule either moderate 
or scanty (Figs. 39 and 59). In few places is it more than 40 inches 
a year, and most of it comes during the spring and summer. The 
fact that most rain falls when temperatures are favorable for plant 
growth is most important. 

Eurasia illustrates the effect on rainfall of distance from the 
windward coast. The western slopes of the British Islands have 80 
to 100 inches of rain yearly; Germany and western Russia have 20 
to 30 inches; eastern Russia and western Siberia, between 15 and 
20 inches; while large areas of central and eastern Siberia have 
less than 10 inches. 

Arid and humid interiors. On the basis of rainfall, there 
are two principal subdivisions of continental climate, the one humid, 
and the other arid. These types merge into each other in a belt 
where the climate is semi-arid. Forests are characteristic of the 
humid climate, but they give place to grass lands where the climate 
is semi-arid, and to deserts where the rainfall is very slight. In a 
general way, moisture decreases with increasing distance from the 
ocean to windward; but topography and cyclonic storms modify this 



i2 4 TYPES OF CLIMATE IN TEMPERATE ZONES 




CONTINENTAL CLIMATES IN UNITED STATES 125 

general relation. Altitude also is an important factor in continental 
climate, especially in arid regions, because highlands increase precipi- 
tation. Lowland deserts may give place to grassy lands at moderate 
altitudes, and to forests still higher. As in tropical deserts, the effect 
of high elevations plays an important part in the life of the arid regions. 

With but slight modification, the continental climates extend 
eastward to the oceans. Ranges of temperature are somewhat less 
near the eastern seaboard, and the rainfall is somewhat greater 
(Fig. 39). 

Continental Climates in the United States 

The interior of our country may be divided into (1) the arid 
region (Fig. 60), chiefly between the Sierra Nevada and Cascade 
mountains on the west and the Rocky Mountains on the east; (2) 




Fig- 
States. 



60. Map showing arid, semi-arid, and humid regions of the United 
(After Newell.) 



the semi-arid region between the Rocky Mountains and longitude 
98 to ioo°; and (3) the humid tract, lying farther east. All these 
regions have extremes of heat and cold. They also have great changes 
of temperature and humidity from day to day as a result of passing 
cyclones and anticyclones. The difference in the amount of rainfall, 
however, makes the conditions of life very different in the three 
regions. 



126 TYPES OF CLIMATE IN TEMPERATE ZONES 

(i) The Arid Region 

The arid region (Fig. 60) includes most of tne Cordilleran section 
of the United States, except the high mountains. Its western margin 
is near the western coast, because the mountains there stop much 
moisture which otherwise would be carried inland by the westerly- 
winds. The average annual rainfall in the arid belt is less than 15 
inches, and over large areas, less than 10 inches (Fig. 59). Sunshine 
prevails throughout the year, relative humidity is low, and evapora- 
tion high. The nights are usually cool even when the days are hot. 
The heat of summer is great, but the humidity is so low that the 
sensible temperatures are not very high. So far as comfort is con- 
cerned, the arid region has an agreeable temperature. 

Effects of scanty rainfall. The scanty rainfall means scanty 
vegetation, except where high elevations cause rain enough to support 
grass or timber. The rapid evaporation of ground-water leaves the 
alkaline substances it contains in the soil, and the slight rains are 
not enough to dissolve and carry these away. In some places this 
gives rise to alkaline soils, unfavorable for vegetation. Where not 
alkaline, desert soils are naturally rich, because elements important 
for plant food have not been leached out or used up (p. 293). Hence 
where water can be applied to desert lands, they are highly productive 
in most cases. 

Many mountains in the arid region receive much snow in winter, 
and this may afford water for irrigation. The total area which can 
be irrigated, however, is but a small portion of the entire arid tract 
(p. 293). Farming is therefore not the leading industry of arid 
lands. Where rainfall is enough to support even a meager growth 
of grasses, grazing is an important occupation. 

Mining is important in parts of the arid West, though aridity has 
little or nothing to do with the development of ores. Desert condi- 
tions favor the accumulation of salt deposits, as about Salt Lake, 
and borax deposits, as in Death Valley, California. 

The population of the arid section is necessarily scanty, because 
there is no natural basis for permanent or extensive settlement in 
most localities. 

(2) The Semi- Arid Region 
In the semi-arid region (Fig. 60), the yearly rainfall is between 
15 and 20 inches (Fig. 50), most of which falls in spring and summer. 






CONTINENTAL CLIMATES IN UNITED STATES 127 

The tract is without high mountains, so that there is little increase 
of precipitation as the result of altitude, and forests are generally 
absent. The region is sunny, and the temperatures are high in 
summer and low in winter. The sensible effects of the extremes, 
however, are moderated by the dryness of the air. The open charac- 
ter of the country favors free circulation of the atmosphere, and 
fairly constant winds of moderate to high velocity are more or less 
typical of most of the region. 

Effect on life. The semi-arid district is a region of grass land; 
there is not enough rain for most cultivated crops. Grazing conse- 
quently has been the most general occupation. Water is highly 
prized, and bitter contests have been waged over the question of its 
ownership. Thus the use of the waters of the Arkansas River, which 
flows from Colorado into Kansas, led to a long legal battle between the 
two stated, because there was not water enough for both. 

(3) The Humid Region 

The semi-arid region merges gradually into the humid region 
farther east (Fig. 60). The temperatures of the two regions are not 
unlike, but in the humid region cloudiness and humidity are greater, 
and evaporation less; hence sensible temperatures are higher in 
summer and lower in winter. The precipitation rarely falls so low 
as 20 inches per year, and most of it comes in summer. The amount 
of rain necessary for crops without irrigation varies with the latitude. 
More is needed in Oklahoma than in Dakota, because the higher 
temperature and lower humidity of the former cause greater evapora- 
tion. In the western part of this region, trees grow in the river 
bottoms; farther east, they become more abundant, and forests are 
found (or were once) over large areas. Throughout the humid region 
there is rain enough for cultivated crops, and it contains some of the 
greatest agricultural tracts of the temperate zones. 

Effects on life. The crops raised are determined largely by 
the climate. Wheat, for example, is raised most in the less rainy 
regions (Fig. 260), and its seed time and harvest are influenced by 
climate. In the north, spring wheat is grown, largely because the 
winters are too cold for wheat sown in the autumn. Farther south, 
where the winter season is shorter and milder, both winter and spring 
wheat may be grown, the former predominating in many sections. 
The harvesting of winter wheat begins in the south in June, and 
the harvesting of spring wheat ends in the north about the first of 



128 TYPES OF CLIMATE IN TEMPERATE ZONES 

September. The harder varieties of wheat, rich in gluten and good 
for macaroni, are grown in the drier sections (p. 366), while softer 
varieties, less rich in gluten, but good for flour, are grown where 
rain is more plentiful. 

The best climate for wheat is one with a dry, sunny harvest season, 
such as that of the Sacramento Valley, California, and eastern Wash- 
ington (p. 121). This ideal climate is not found in much of the 
humid interior, where wheat is the standard crop only in a north- 
south belt, some ten degrees in width, just east of the 100th meridian. 
Even here, the climate is not so good for wheat as that of eastern 
Washington. 

East of the wheat belt, the heavier rains favor a variety of crops. 
Corn is the standard cereal in great areas (Fig. 259), though wheat, 
oats, and other crops are commonly grown in rotation with it. Corn 
is not grown so far north as wheat, because corn requires a higher 
temperature, and most varieties require a longer warm season. With 
corn, many other cereals, vegetables, and fruits are grown, requiring 
more moisture than wheat. 

The humid continental region is the region of greatest develop- 
ment in the United States. It has the major part of the population 
(Fig. 281), it contains most of the chief cities (p. 399), its manufactur- 
ing and commercial activities are greatest (p. 383), and its transpor- 
tation facilities are best (Fig. 279). All these things reflect the 
abundant yield of the soil, and this is a result, in large part, of favor- 
able climate. 

The abundance of rain and the topography of the eastern coast 
of the United States favor the development of swamps, and in low 
latitudes swamps invite diseases like those of equatorial regions 
(p. 103). The home of malaria in the United States is on the low 
plains and in the river valleys along the eastern coast south of New 
York. Yellow fever has been introduced many times into the 
Gulf and South Atlantic ports, but could not last from one summer 
to the next, on account of the frosts of winter. 

Shore towns in nearly all latitudes feel the beneficial effects of the 
sea-breeze (p. 74), and many important seashore resorts from 
New Jersey northward are the result. In the higher latitudes, the 
ocean affects the temperature of coastal lands chiefly by lowering 
the temperature in summer, because of frequent winds (sea-breezes 
and cyclonic winds) from the east. The July mean for Labrador, 
for example, is 13 or 14 lower than that for Norway House, at the 



IMPORTANCE OF HUMID REGIONS 129 

northern end of Lake Winnipeg, near the great Canadian wheat 
district. In Labrador none of the cereals will ripen. The sparse 
population there finds its chief support in fishing, hunting, and 
trapping. Fishing especially is important during the summer, and 
when the catch is small, the people suffer greatly from want during the 
long, cold winter. 

The same factors which lower the temperature and increase the 
rainfall along our eastern coast increase cloudiness and fog. Places 
exposed freely to the sea (like Newfoundland) have conditions of 
humidity, cloudiness, and fog similar to those of marine climates on 
western coasts. Along the eastern coast, therefore, the continental 
climate is somewhat modified. 

The humid parts of the north temperate zone are the greatest 
cereal districts of the world. They bear the same relation to the cul- 
tivation of cereals that the semi-arid steppe lands, with their grassy veg- 
etation, hold to the live stock industry of the world. Thus the great 
wheat regions lie mainly between the 40th and 55th parallels. Rye, 
closely related to wheat in its uses and conditions of growth, replaces 
wheat in many places where the soils are too poor for the latter. 
Of the other great cereal crops in this belt, oats and barley are grown 
more to the north, and corn to the south. Hence, through the heart 
of the temperate zone is found the home of all the cereals, save rice, 
which serve as food for man. This arrangement of important crops 
influences both the distribution of population and the movement of 
commerce. The populous part of the temperate zone corresponds 
closely to the cereal belt. Much of the commerce of the world now 
moves along east and west routes in these same latitudes. No other 
country is situated so well as the United States with respect to 
cereal growing lands. 

The whole humid section in the interior of this country is exposed 
to sudden frost in late spring and early autumn (Fig. 61), and in 
either case widespread damage may result. Its southwestern part 
is exposed to hot winds from the south which, in exceptional cases, 
wither and kill crops. Droughts are common, though less frequent 
and less widespread than in monsoon countries. Almost every 
year some part of the humid portion of the United States suffers 
from too little rain; but severe drought rarely affects a great area, 
or the same area frequently. In monsoon countries like India, on 
the other hand, a large area suffers from drought at the same time, 
and the same area may suffer for a period of years. Tropical and sub- 



130 TYPES OF CLIMATE IN TEMPERATE ZONES 

tropical Australia also has frequent and long-continued droughts which 
affect large areas. In spite of its extremes of climate, central and 
eastern United States is a highly favored agricultural region, largely 
because of its reliable rainfall. 

Near the northern limit of the north temperate zone the summers 
of interior lands are too short and too cold for cereals. Even in the 
most favored parts of continental interiors, the hardiest cereals cannot 



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Fig. 6i. Map of United States showing average dates of last killing frost in 
spring (broken lines) and first killing frost in autumn (solid lines). (After U. S. 
Weather Bureau.) 

be grown much beyond the 6oth parallel (Fig. 58). Dense forests 
disappear in most places before the margin of the zone is reached, 
being replaced by the scattered trees and scanty vegetation which 
mark the beginning of the frozen, polar wastes. Both Canada and 
Russia have large areas of this nearly worthless, almost uninhabited 
territory (p. 336). The United States, on the other hand, is neither 
too far north nor too near the equator. Climatically, it has the best 
position of any large country. 



4. MOUNTAIN CLIMATES 

Temperature. Even moderate altitudes so affect temperature 
as to determine what crops may be cultivated. For example, in 



MOUNTAIN CLIMATE 131 

the plateau sections of Pennsylvania, in latitude 40 to 42 , corn can- 
not be depended on to ripen at an altitude of 2,000 feet. In some of 
the drier, hence warmer (in summer) and sunnier, parts of the arid 
West, corn, under irrigation, will ripen at much higher altitudes 
(4,000 feet about Great Salt Lake). In general, the upper limit for 
even the hardiest crops does not exceed 6,000 feet, even in the lower 
latitudes of the temperate zone. In contrast, corn is grown in 
Bolivia at an altitude of 10,000 feet, and wheat even higher. The 
timber-line (upper limit of timber) in the United States ranges from 
an altitude of about 11,000 feet at the south, to 7,000 or 8,000 at the 
north, and the level at which snow lies most of the time is not far above 
these limits. Hence, so far as agriculture is concerned, the higher 
lands of the temperate zone are of little use. 

Precipitation. The effect of altitude on rainfall is the same 
in the temperate zone as elsewhere. It increases the amount of 
precipitation, and tends in many cases toward a maximum in winter. 
The increased precipitation at higher altitudes usually results in 
heavy snowfall in winter. Thus Baltimore, altitude 104 feet, has 
an average of 23.8 inches of snow annually, while Grantsville, Md., 
altitude 3,400 feet, has 71.2 inches. Summit, the top of the pass 
(7,017 feet) crossed by the Southern Pacific railroad east of Sacra- 
mento, Cal., has an average snowfall of 433 inches a year, and twice 
in thirty- three years the amount has reached 775 inches. Sacramento, 
on low land to the west, has only a trace of snow each year. 

Winter snowfall is an important factor in the flow of many rivers. 
Disastrous winter and spring floods are the result in some cases 
(p. 76), and in others the supply of water from melting snow is an 
important aid in (1) the development of water power, (2) the main- 
tenance of a sufficient depth of water for navigation, and (3) irrigation. 
Heavy winter snows and snowslides offer serious problems to railroad 
lines which run at high levels, and at the bases of mountains. Snow- 
slides are one of the things to be feared about mines in mountains, 
and mountain villages have been destroyed by them. 

Mountain conditions of temperature and rainfall favor forests, 
and make many mountains the sites of lumbering (p. 316). Forest 
trees thrive far' above the altitudes which limit crops. Even in 
arid regions, some areas 5,000 to 6,000 feet high have rain enough 
to support forests of commercial value. 

Many mountains serve as health and pleasure resorts (p. 317). 
Most mountain health resorts are visited chiefly by persons afflicted 



i 3 2 TYPES OF CLIMATE IN TEMPERATE ZONES 

with diseases of the lungs, especially tuberculosis. Mountain climate 
is not a cure for this disease; but the conditions in the mountains 
may aid in checking it, or may even enable the organs affected to 
throw it off. The favorable conditions are (i) the pure, dry air char- 
acteristic of the higher altitudes of many mountains, and (2) the de- 
creased density of the atmosphere, which stimulates the lungs to 
greater activity. In the arid parts of western United States, these 
conditions are associated with bright, sunny weather, which favors 
out-of-door life. 

Questions 

1. Explain the absence of summer rainfall in sub-tropical climates, even with 
winds from the ocean. 

2. Account for the morning fogs of the coast of southern California in summer. 

3. Why is the Pacific Ocean not the chief source of moisture for the United 
States? 

4. Explain the differences in climatic conditions at different points on the 
41st parallel in the United States. Along the 32nd parallel. 

5. Explain the increase in rainfall from San Diego northward to Astoria. 
(See Fig. 59 and Plate II.) 

6. Why are the limits of cereals and of permanent habitations nearer the 
equator in Fig. 57 than in Fig. 58? 

7. How does the isotherm of 50 in Fig. 57 differ from that of Fig. 58? Why? 

8. Why do the lines showing average dates of frost (Fig. 61) turn northward 
over Lake Erie and along the south Atlantic coast? 

9. W 7 hy is the snowfall in the Mississippi Valley heavier than that in the 
corresponding latitudes on the Atlantic coast? 

10. Suggest reasons, based on climate, why there is little commerce between 
lands of the south temperate zone. 



CHAPTER XI 
CLIMATE OF POLAR REGIONS 

General Considerations 

Extent of polar regions. The limits of the polar regions are 
commonly placed at the Arctic and Antarctic circles; but they are 
sometimes regarded as being limited equatorward by the isotherm of 
50 for the warmest month, an isotherm which marks the approxi- 
mate limit of the growth of trees and cereals (Fig. 62). In this dis- 
cussion, the latitude division is used. Thus defined, the polar regions 
have an area about one-twelfth that of the earth. 

General features of polar climate. All polar regions are alike 
in having the sun above the horizon for more than twenty-four con- 
secutive hours, and below the horizon for a similar period, once 
each year. Near the margins of these zones, the longest period of 
continuous sun is only a few days (of 24 hours each) ; but the time 
during which the sun does not set increases poleward, and at the 
poles the day (period of continuous light) is six months long (p. 43). 
During the period of continuous light, insolation is greater in polar 
regions than in low latitudes (p. 35), but the temperature of the lower 
air is not raised accordingly, because (1) the sun 's rays are very oblique 
(Fig. 21), and (2) much of the heat which reaches the surface melts 
ice and snow, and is not effective in warming the air. The result is a 
low temperature for the year, and, except for lands free from snow and 
ice, a low temperature at all times of the year. 

Temperature. Many of the recorded temperatures of January 
in the Arctic region range from — 40 to — 6o°, while the warmest 
month has an average temperature of 32 or more in many places. 
The maximum summer temperatures close to the margin of the zone 
are locally as high as 8o°, or even 90 ; but such temperatures occur 
only where there are large areas of land free from snow and ice. Most 
of the Antarctic region has a summer temperature below the freezing 
point even during the warmest month, so far as present records show. 

The annual range of temperature in the Arctic region is greater 

133 



134 



CLIMATE OF POLAR REGIONS 



than that in the Antarctic, because more land in the former is without 
snow and ice in summer. Verhoyansk, in Siberia, just within the 
Arctic Circle (Lat. 67 6'), has a July mean of +6o° and a January 




Fig. 62. Map of North Polar Zone, showing land and water areas. Pole- 
ward limit of growth of cereals Poleward limit of growth of forest trees 

. Poleward limit of permanent habitations + + + +'+. Isotherm of 50 for 

warmest month . 



mean of — 6o°. In contrast, Hammerfest (Lat. 70 40'), on the 
coast of Norway, and the most northerly town in Europe, has a Janu- 
ary mean of 23 , and a July mean of 53 . Hammerfest shows the full 
effect of the ocean on the temperature of windward coasts in high 
latitudes. 



THE LIFE OF ANTARCTIC REGIONS 135 

Humidity arid precipitation. The low temperatures affect the 
other elements of climate. They mean little evaporation, and hence 
little moisture in the air. The relative humidity varies from extreme- 
ly low, especially far from the sea to windward, to relatively high, 
particularly on windward coasts. The precipitation is light, prob- 
ably averaging less than 1 5 inches a year except on windward coasts. 

The Shackleton expedition to Antarctica found, from recording instruments 
left by a preceding expedition, that the average precipitation for six years had been 
the equivalent of 7 to 8 inches of rain. Most of the precipitation in polar regions 
is in the form of snow, and is frequently accompanied by violent winds. Rain is 
said to fall in most parts of the north polar region during the warmer months. In 
the south polar region the Shackleton expedition found all precipitation during 13 
months to be in the form of snow. 

The great fields of snow and ice in the polar regions are not due 
to heavy snowfall, but to the preservation of most of that which falls. 

In summer, fogs are common, and are a great hindrance to navi- 
gators. 

The Antarctic Region 

The Antarctic region is largely ice-covered water and ice-covered 
land. The scattered land areas which have been discovered are 
probably parts of an Antarctic continent. Beyond the edge of this 
ice-covered land the surface rises toward the interior to heights of 
several thousand feet. 

If the south polar region were limited by the isotherm of 50 for 
the warmest month, it would include everything south of the 55th 
parallel. 

Temperature. The great expanses of ice and ice-water do not 
allow the temperature of this zone to rise much above 32 , even in 
summer. During this season, fog and cloud are so frequent that much 
insolation is cut off. Fogs and clouds are therefore important factors 
in keeping the summer temperatures low. 

The mid- winter (July) temperatures of the lower latitudes of this 
zone are about — 15 to — 20 , so far as recorded. The temperatures 
of higher latitudes are probably much lower. The seasons between 
winter and summer are very short. The one shows a rapid rise from 
the low temperatures of winter, and the other a rapid drop from the 
temperatures of summer. 

Effects on life. The Antarctic region is without most kinds of 
vegetation familiar to us. Some mosses and lichens are found on such 



i 3 6 CLIMATE OF POLAR REGIONS 

lands as are free from ice for a part of the year, but no form of vegeta- 
tion useful to man is known. The animal life is mainly marine, whales 
and seals being characteristic. The waters abound in lower forms of 
life, such as molluscs and still simpler types. On land, animal life is 
represented by a few species of birds and insects. Great rookeries of 
penguins form one of the most remarkable assemblages of bird life to 
be found anywhere. The albatross, gull, and some other kinds of 
Sea-coast birds also are found. From the standpoint of life in general, 
however, the Antarctic lands are as close an approach as there is to 
an absolute desert. 

The Arctic Regions 

In the higher latitudes the Arctic Ocean is covered with ice most 
of the year, though the ice is more or less broken in summer. In 
the lower latitudes much of the ocean is free from ice all or part of the 
time. Snow and ice cover all but the fringe of Greenland, and the 
larger part of many other islands. The Arctic portions of the conti- 
nents are not covered by ice and snow during the summer, and their 
climate is in sharp contrast (How?) with that of regions which are so 
covered. There is also a great contrast between the interior lands 
which are snow-free during the summer, and windward coasts, such 
as western Alaska and northwestern Norway, which are affected by 
the moderating influence of winds from the oceans (p. 134). 

Temperature. The temperatures of this zone vary widely. 
The lowest yearly temperatures are found where there is a permanent 
covering of ice. Such observations as are recorded indicate a January 
mean of about — 40 for northern Greenland, while its July mean 
is near the melting point. The continental interior of Siberia is 
even colder than Greenland in winter. In summer, however, this 
same region, being without snow or ice, becomes very much warmer 
than Greenland. 

Arctic lands free from snow in summer have great extremes of 
temperature, and summer maxima of 6o° to 8o° are almost typical 
of the margin of the zone. Temperatures of 90 or more are reported 
frequently from Alaska and Siberia. An extreme range of 150 for 
the year is common, and the highest summer and lowest winter tem- 
peratures recorded are more than 180 apart. 

The extreme and long-continued cold of winter is sufficient to freeze 
the water in the ground to the depth of scores of feet, and the tempera- 
tures of summer suffice to melt the ice in the top part only of the soil. 



LIFE IN ARCTIC REGIONS 137 

Plant life. The relatively high temperatures which prevail on 
ice-free land in summer permit the growth of many kinds of plants. 
As compared with the temperate zone, however, the amount and 
variety of vegetation are meager. Stunted trees of the hardier 
types, such as larches, pines, birches, and willows, grow near the border 
of the Arctic zone (Fig. 62). The northern limit of these trees is near 
the 70th parallel in Siberia and northwestern Canada. Dwarf willows 
and birches (hardly trees) are said to occur 8° or io° farther north. 
Mosses, lichens, and other low types of plants abound in the Arctic 
tundra, which becomes a sea of mud as it thaws out during the sum- 
mer. In the dry places in the tundra, and on southerly slopes where 
drainage of the soil is good and where insolation is great, there are 
many flowering plants, some of which produce berries. On the west 
coast of Greenland, poppies grow north at least to latitude 78 . The 
plants of these high latitudes are rapid growers, as the short growing 
season would let no other plants mature. 

The temperatures of air and soil exclude crops from nearly all the 
polar region. There are a few localities, as in northern Norway and 
favored spots in Alaska and Siberia, where hardy cereals and some 
vegetables may be grown (Fig. 62). 

Animal life. Animals, as well as plants, are more abundant 
in the Arctic regions than in the Antarctic. Sea life is more abundant 
than land life. The larger sea animals are similar to those of the 
Antarctic, and include whales, seals, and walruses. All these animals 
are important to the people living in the Arctic region, and are the 
basis for certain industries carried on from places in lower latitudes. 
Thus, sealing and whale fishing are carried on close to the Arctic Cir- 
cle, and even within it. The Arctic seas also teem with smaller forms 
of life, such as molluscs and small crustaceans. Birds are prominent 
in the summer. The little auk, dovekies, guillemots, and (locally) 
the eider duck abound. Among land mammals, the reindeer, fox, 
hare, polar bear, and musk-ox may be mentioned. 

Arctic people. The Arctic region, unlike the Antarctic, is in- 
habited by human beings, the best known of whom are the Eskimos 
(Fig. 62). The population, however, is scanty, scattered, and, on the 
whole, not highly civilized. Along the southern margin of the zone, 
there are many small groups of people. Farther north, the groups 
are fewer and smaller, and more confined to coasts. The most 
northerly permanent settlements are on the west coast of Greenland, 
the northernmost, Etah, being above the 78th parallel. 



138 CLIMATE OF POLAR REGIONS 

For all inhabitants of polar regions, life is a constant struggle. 
The cold means poverty of resources, a constant fight for food and 
clothing, and consequent inability to progress. Edible plants are 
absent, except in the lower latitudes of the zone, and for a short time 
each year. Land animals, like the reindeer, are comparatively scarce 
on account of the meager vegetation. Hence the people depend in 
large part on marine life, and most of them live along the coasts. 

Meat is the principal food, and is furnished by the seal, the walrus, 
and fish, supplemented by the reindeer, the hare, the bear, and birds. 
Most of this food can be obtained only during the time of light, which 
is therefore the hunting season. Food for winter is preserved easily 
because of the cold. Since fuel and means of cooking are meager, 
much meat is eaten raw. In north Greenland, the tiny fire — a 
little oil with a wisp of grass or moss for a wick — is used chiefly for 
melting snow and ice for drinking water. The dependence of the 
people on animal life makes them hunters and fishers. The hunters 
are partly nomadic, going about in search of game during the sum- 
mer, but having fixed habitations for winter. 

Most of the Eskimo 's clothing is of fur. Plant fibers which could 
be woven or braided together are unknown, except as they are brought 
in from other lands. The materials used in making dwellings depend 
on local circumstances. Where forests are accessible, as along the 
margin of the zone, or where driftwood can be had from the ocean, 
as along some coasts, wood is used. Elsewhere, the winter house is 
usually of stone or snow. During the hunting season, the hunters 
live in tents of skins. 

Weapons and utensils may be made from wood, if it is available; 
more commonly they are made from bone and hides. The use of these 
animal products is the characteristic feature of the arts and crafts of 
the Eskimos. Perhaps in no other thing is their skill shown better 
than in the making of their kayaks (boats), where the only materials 
to be had are bone, pieces of driftwood, and hides. Out of these they 
fashion a craft wonderfully adapted to the uses to which it is put. 

Looked at with reference to their surroundings, the Eskimos 
hardly can be regarded as backward. Probably they make better 
use of the things at their command than more highly civilized men 
could, but Arctic climate is too great a handicap to allow them to 
progress far. 



QUESTIONS 139 



Questions 

1. Why is rainfall relatively unimportant in affecting the distribution of 
people in the polar regions? 

2. If the entrance from the Pacific to the Arctic Ocean were widened greatly, 
what would be the probable effect on the climate of polar North America? 

3. Suggest reasons why the Antarctic has been less well explored than the 
Arctic regions. 

4. Why do trees grow in higher latitudes in Asia than in North America 
(Fig. 62)? 

5. What factors determine the course of the isotherm of 50 in Fig. 62? 

6. Why is there an ice-cap over central Greenland and not over lands in the 
same latitude in northern Asia? 



CHAPTER XII 
THE OCEANS 

General Considerations 

Importance of the oceans. The oceans are of great importance 
to the rest of the earth in many ways. Their effects on temperature 
and atmospheric moisture have been noted (pp. 51, 57). The waves 
of all seas are constantly wearing away the land in some places, and 




^>i 



Un.King. $ 550 29.5' 
Germy 258 13.8* 
France 115 6.2* 
Nether. 84 45* 
Italy 52 2& 
Other 120 71 = 

n 




Austral. $3 

Japan 26 14* 

Phil.Ts. 19 I.O* 

China 15 OS* 

India 7 oa' 

Other 23 13< 



Argent *42.7 23* 

Brazil 24.9 1.5* 

Chile 9.9 05* 

Other 22.5 t2* 



Y- 



Br.S.APr. $11.4 CXfe' 
PortAfr. 3.4 0.2< 
Br.WAfr. 2.5 
Egypt 13 
Other 25 



w° 




Fig. 63. Diagram showing destinations of exports from the United States 
by continents and leading countries (1910). (Values in millions of dollars; per- 
centages are proportions of total exports.) 

building new land elsewhere. On the whole, destruction exceeds 
building, so far as land is concerned; consequently, the ocean tends 
to increase its area at the expense of the land (p. 348). 

The oceans are an important source of food, and furnish large 
amounts of other useful materials. Thousands of people are em- 

140 



COMMERCE OVER THE OCEAN HIGHWAY 141 

ployed in getting commercial products from them. Other thousands 
are engaged in the carrying trade on the seas. Formerly the 
oceans were barriers to travel and communication, but swift steam- 
ships and cable lines now make communication between the con- 
tinents easy. The voyage across the Atlantic formerly took as 
many weeks as it now takes days, while the happenings of this 
morning in Europe may be printed in the evening papers of Buenos 
Aires. Nine-tenths of our foreign trade is carried by vessels. 
Enormous quantities of goods are shipped annually to the United 
States from all the leading countries of the world, and from the 
United States to these countries (Figs. 63 and 64), over the ocean 
highway. 

Distribution and area. The oceans encircle the earth in latitude 
6o° S. (Fig. 57), and the waters south of 40 S. are sometimes called 




Fig. 64. Diagram showing sources of imports to the United States by con- 
tinents and leading countries (1910). (Values in millions of dollars; percentages 
are proportions of total imports.) 



the Southern Ocean. From it the Atlantic, Pacific, and Indian oceans 
extend northward thousands of miles. In the northern hemisphere 
the land makes an almost complete circuit in latitude 6o° to 70 (Fig. 
58), whence it extends southward in two great arms. North of 
latitude about 70 lies the Arctic Ocean, almost surrounded by land 



i 4 2 THE OCEANS 

(Fig. 62) and therefore with but narrow connections with the larger 
oceans. The area of the different oceans is about as follows : 

Arctic Ocean 5,200,000 square miles 

Indian Ocean 28,000,000 square miles 

Atlantic Ocean 35,000,000 square miles 

Pacific Ocean 67,000,000 square miles 

Southern Ocean 5,700,000 square miles 

Exploration of the ocean. The motions of the surface waters; 
such as waves and tides, may be studied from the shore, but it has 
taken the work of many exploring expeditions to give us our present 
knowledge of the depths of the ocean. 

The depth of the ocean is known by soundings, which are made 
from ships by reeling out a heavy weight held by a fine steel wire. 
A sounding of 3,000 fathoms (a fathom = 6 feet) can be made in about 
an hour. A series of soundings in any region give a fairly accurate 
idea of the form of that part of the sea-floor. 

Small samples of sediment from the bottom of the sea are brought 
to the surface by various sorts of apparatus. Larger samples of 
material from the bottom and specimens of deep-sea life are obtained 
by dredges. Another device, known as a water-bottle, is used to 
secure samples of water from various depths, while a self-registering 
thermometer records the temperatures at different levels. 

Materials of the bottom. Most of the sea-bottom is covered 
with soft sediment. Some of it was carried to the sea by rivers, some 
was worn from the shores by waves, some was blown from the land, 
some is made up of the shells and skeletons of organisms which lived 
in the water, and some consists of fine debris thrown out from vol- 
canoes beneath the sea. A little cosmic (" shooting-star") dust is also 
present. Near many shores, gravel and sand from the land cover the 
bottom. Beyond the gravel and sand, fine sediments, such as mud 
and clay, prevail; but sediments of organic origin are found in many 
places. Thus coral reefs and mud made by the grinding up of coral 
by waves are found in shallow water in many places in low latitudes. 

Ooze is the name applied to those soft materials of the sea-bottom composed 
largely of the shells and other hard secretions of tiny organisms which live in the 
water. Many of them live near the surface, and their shells sink when the organ- 
isms die. The various oozes are named from the animals and plants which con- 
tribute most to them. 

Below the depth of about 2,200 fathoms, the ocean-bottom is 
covered with red clay, the particles of which came from many sources. 



THE DEPTHS OF THE SEA 143 

Most of it consists of the decomposed products of (1) materials 
thrown out from volcanoes, (2) dust blown from the land, (3) shells 
and other hard parts of marine life, and (4) meteors. 

Depth and pressure. The average depth of the ocean is about 
two and one-half miles, or nearly 13,000 feet. The depth exceeds 
four miles in many places, and the area of very deep water is much 
greater than that of very high land. The areas which are far below 
the average depth of the ocean are known as deeps. The greatest 
depth of water known, 32,078 feet, is in the Pacific Ocean, near the 
Philippine Islands. This depth is more than the height of the highest 
mountain (Mt. Everest, 29,002 feet) above the sea. There are other 
areas exceeding five miles in depth in the Pacific, which is the deepest 
ocean. The greatest depth of water known in the Atlantic is Blake 
Deep (27,366 feet), north of Porto Rico. In few other places in the 
Atlantic does the depth reach 20,000 feet. The Indian Ocean is not 
known to have depths much exceeding 20,000 feet, and the deepest 
known places in the Arctic and Antarctic seas are still less. 

The pressure at the bottom of the oceans is very great. At a 
depth of one mile, it is about a ton to the square inch, while in the 
greatest depths it is six tons. This pressure would crush some kinds 
of stone. Yet the ocean water does not become much denser (is not 
compressed much) even under so great pressure. Objects such as 
pebbles, which sink readily at the surface, sink readily to the 
bottom. 

Topography of the bottom. The surface of the land is made 
rough in various ways, especially by running water and winds; but 
most of the sea-bottom is nearly flat. In spite of its general flatness 
the sea-bottom has many irregularities, for there are (1) volcanic cones, 
some of them built up from the bottom of the deep sea to elevations 
far above its surface (p. 194) ; (2) steep slopes, such as those (a) between 
the continental platforms and the deep-sea basins and (b) about some 
of the deeps; (3) valley-like depressions, especially on the continental 
shelves; (4) great ridges somewhat like the mountain ridges of the land; 
and (5) broad, plateau-like swells. Submarine slopes as great as 1 
mile in 8 are rare, and 1 mile in 20 not very common. The latter 
would make a steep railway grade. 

Volcanic cones are most numerous in the Pacific Ocean. Many of the valley- 
like depressions on the continental shelves are continuations of valleys on land. 
Thus the Hudson, Delaware, Susquehanna, St. Lawrence, and other valleys are 
continued out under the sea. Such submerged valleys are thought to have been 



144 THE OCEANS 

formed by rivers when the areas where they occur were land. Examples of moun- 
tain-like swells are furnished by Cuba and the adjacent islands, which are really 
the crests of a great mountain system rising from deep water. 

Composition of sea-water. One hundred pounds of average 
sea-water contain nearly three and one-half pounds of dissolved 
mineral matter. More than three-fourths (nearly 78 per cent) of 
this is common salt, but nearly all other substances found in the 
earth's crust are present, most of them in very small quantities. 
If all the salts dissolved in the sea were taken out of solution and laid 
down as solid matter on the ocean-bottom, they would make a layer 
about 175 feet thick. In the past, the evaporation of water from 
salt lakes, perhaps cut off from the sea by changes of level, has formed 
important salt-beds. New York has a valuable salt industry near 
Syracuse, depending on such deposits of rock salt (p. 183). 

The mineral matter in sea-water makes it a little heavier than 
fresh water, and makes it freeze less readily. Its lower freezing point 
(26°-28° F.) often leaves the ocean free from ice when nearby bodies 
of fresh water are frozen over. 

Sources of mineral matter. Dissolved mineral matter is being 
carried to the sea by rivers all the time, and they have brought the 
sea most of its mineral matter, though some of it may have been dis- 
solved from rocks beneath the sea, or about its shores. The mineral 
matter carried in solution to the sea by rivers in a year would make 
nearly half a cubic mile of solid matter. Those minerals of the land 
which are dissolved most easily get into rivers, and thence to the 
sea, in greater quantity than those which are less soluble. 

Withdrawal of mineral matter from the sea. Of the mineral 
matter carried in solution to the sea, calcium carbonate, of which 
most shells are made, is most important to ocean life. The amount of 
this substance dissolved in river-water is nearly as great as that of 
all others. The amount of common salt in river-water is too small 
to be tasted; yet the amount of it in sea- water is more than 200 
times that of calcium carbonate. The reason is that calcium carbon- 
ate is taken out of the water all the time by animals, to make shells, 
coral, etc., while most of the salt carried to the sea stays in the water; 
and this probably has been true for millions of years. 

Gases in sea-water. Sea-water also contains dissolved gases, 
the most abundant being nitrogen, oxygen, and carbon dioxide. The 
amount of oxygen dissolved in the ocean is more than V300 of that 
in the air; the amount of nitrogen about Vioo that of the air, 



TEMPERATURE OF THE SEA 145 

while the amount of carbon dioxide in the sea is 18 times that in 
the air. Much of the gas in the ocean was dissolved from the 
atmosphere. 

The oxygen of the water is being used all the time by sea animals, 
and its supply is being renewed all the time by solution from the air. 
Animals and plants do not use the nitrogen dissolved in sea-water, 
and the same nitrogen probably stays there from age to age. The 
carbon dioxide is being used all the time by the plants of the sea, and 
some of it is constantly escaping into the air. 

Salinity, density, and movement. For several reasons, some 
parts of the sea are more salty than others. (1) The salt is left behind 
when ocean- water evaporates. Since evaporation is more rapid in 
some places than in others, the water becomes more salty where 
evaporation is great, as in some hot climates. (2) Where much rain 
falls, and (3) where large rivers enter, the sea- water is freshened. 
In these ways the saltness of the sea- water at the top of the ocean is 
changed all the time. 

Every change in the saltness of sea-water changes its density, and 
unequal density causes movement. When surface water becomes 
denser than that beneath, it sinks, and lighter water comes in over 
it from all sides. When the surface water of one place becomes less 
dense (fresher) than that about it, the lighter water spreads out on 
the surface, as oil spreads on water. Since variations in saltness are 
being produced all the time, motion due to unequal density is constant. 
Movements brought about in this way are usually very slow. 



Temperature of the Sea 

Temperature of the surface. The surface of the ocean, like 
that of the land, is warmer near the equator and cooler toward the 
poles (Fig. 65). Near the equator its temperature is about 8o° F.; 
near the poles, where not frozen, it is 26°-28° F. When frozen, the 
surface of the ice may become as cold as the air above it; but the tem- 
perature of the water just beneath the ice is 26 — 28 F. The de- 
crease of temperature toward the poles is by no means regular, as 
shown by the isothermal chart (Fig. 65). 

In the open .sea, ocean currents help to make the isotherms 
depart from the parallels (p. 51). Some currents are cold, flow- 
ing into warmer water, and some are warm, flowing into cooler 
water. 



146 



THE OCEANS 



Rivers help to make surface temperatures unequal, for many of 
them are warmer than the sea in summer, and colder in winter. Part- 
ly enclosed arms of the sea in low latitudes are warmer than the open 
ocean in the same latitude. 

Temperature and movement. Water expands slightly when 
warmed. Warm water is therefore lighter than cold water, if both 
are equally salt. It follows that unequal surface temperatures cause 
movement of the surface waters, and since the surface temperature 
is kept unequal all the time by unequal heating, by inflow of rivers, 




Fig. 65. Map showing mean annual temperatures for the surface waters of 
the oceans. (After Lyde.) 



and by melting ice, there is constant though slow movement of the 
surface waters. 

Temperature beneath the surface. Sea-water becomes cooler 
with increasing depth, except where the surface is at or near the 
freezing point. Even where the surface water is warmest, the 
temperature at a depth of a few hundred fathoms is below 40 F. 

It is estimated that not more than one-fifth of the water of the 
ocean has a temperature as high as 40 F., while its average tempera- 
ture is probably below 3c) F. Only in certain areas of shallow water, 
and in the partly enclosed seas of relatively low latitudes, is the tem- 
perature of the water at the bottom as high as 40 . 



WAVES, CURRENTS, AND TIDES 147 

Movements of Sea- Water 
Causes 

We have seen that differences in saltness and in temperature 
make waters unequal in density, and so produce a slow circulation of 
the waters of the sea. There are other things which produce move- 
ment, such as (1) differences of level, (2) winds, (3) the attraction of 
the moon and the sun, and (4) occasional causes, like earthquakes 
and volcanic explosions. 

Inequalities of level. The inequalities of level which produce 
movements of sea- water are brought about chiefly by (1) the in- 
flow of rivers, which raises the surface of the sea near their mouths; 
(2) winds, which pile up the water along the shores against which 
they blow; (3) unequal rainfall, which raises the surface most where 
most rain falls; and (4) unequal evaporation, which lowers the sur- 
face most where it is greatest. 

Movements due to unequal rainfall and evaporation are too slight 
to be seen. Those caused by the inflow of rivers and by winds are 
greater. Thus, beyond the mouth of a great river like the Amazon, 
movement may be distinct for many miles, and waters often are piled 
up against a shore by winds, so that the rise is seen readily. The 
raising of the surface of the water caused most of the destruction in 
the storm at Galveston (p. 92). When the water-level along a coast 
has been raised by the wind, it settles back after the wind goes down. 
Since the causes producing differences of level are always in operation, 
movements due to these differences are always taking place. 

Winds. Winds produce movement of sea-water in another way. 
Where they have a constant direction, as in the zone of trades (p. 105), 
there is a constant drifting movement of surface water in one direc- 
tion. A steady movement in one direction necessitates a return move- 
ment somewhere else, thus producing a circulation of the sea-water. 
Where the circulation is in the form of distinct streams of water, they 
are called ocean currents. 

Attraction of moon and sun. Bodies attract each other in 
proportion to their masses, and inversely as the squares of their 
distances. That is, a body which weighs twice as much as another 
has twice the attractive force at the same distance. If one of two 
bodies of the same mass (or weight) is twice as far from a third body 
as the other is, their attractive forces on the third are as 1:4. 

The side of the earth toward the moon is nearer the moon ( by 



148 THE OCEANS 

about 4,000 miles) than the center of the earth is, and so is attracted 
by that body more strongly than the center. The opposite side (about 
4,000 miles farther away) is attracted less strongly than the center, 
and these differences of attraction disturb the waters of the earth. 
The attraction of the sun produces similar, though lesser, effects. 
Movements of the sea-water, known as tides, are the result. 

Occasional causes. Landslides along shore, earthquakes, and 
volcanic explosions may cause sudden and extensive movements of 
the ocean-water (pp. 191, 197). Low coastal lands occasionally 
suffer severely from movements of this sort. 

Types of Movement 

The principal movements which result from the above causes are 
(1) waves, with the undertow and shore currents (p. 346) which they 
produce; (2) ocean currents; (3) drift, or feeble currents; and (4) tides. 

Waves. When the wind blows over a water surface it causes 
waves. The stronger the winds, the greater the waves. With 
moderate winds, waves in open water rarely exceed 10 feet in height 
(from crest to trough). Ordinary storm-waves may be twice as high, 
while in violent storms a height of 40 or more feet is attained. Such 
waves breaking on the decks of vessels may do much damage. Storm- 
waves travel 30 to 60 miles an hour, but, save in shallow water, the 
water in a wave usually does not move forward (p. 346). 

The distance between successive wave crests is the length of the 
wave. Wave lengths vary from 100 feet or less, to 2,000 feet or more 
in severe storms. Occasionally the surface of the ocean is smooth and 
glassy, and yet shows long, low undulations. These are "swells," 
and usually represent waves caused by distant storms. On some 
coasts they interfere seriously with commerce. Short, "choppy" 
waves are especially unfavorable for small craft, and may cause much 
discomfort to passengers on larger vessels. In general, the longer the 
vessel, the less it is affected by waves; hence the advantage of the 
modern ocean steamships, which in many cases are twice as long 
(700 to 800 feet) as the average storm-wave. 

Currents and drifts. There are more or less distinct streams 
of water, or currents, in various parts of the ocean. This was known 
first by their effect on the course of sailing vessels. It was later proved 
in other ways, as by following the course of floating objects set adrift 
for this purpose. 

The course of currents is important because of their effect on navi- 



THE GULF STREAM 149 

gation. In foggy weather, and especially near some coasts, failure to 
allow for the current may lead to ship-wreck. Some of the wrecks 
that have occurred on the Irish coast probably were caused in this 
way. Vessels are aided or retarded by currents, according to the 
direction of the voyage. Surface currents affect the movements of 
icebergs and floe-ice. Collision with an iceberg may wreck the 
largest steamship, as the Titanic, and floating ice favors the forma- 
tion of fog, which increases the danger of collision. For these reasons, 
steamship routes across the North Atlantic vary somewhat with the 
season, in order to avoid the floating ice. 

Little is known of ocean currents beneath the surface. Most of 
them are shallow, compared with the depth of the ocean. A current 
so slow as to be indistinct often is called drift. 

Courses and causes of ocean currents. Fig. 66 shows the 
general circulation of the surface waters of the sea. It represents a 
large part of the surface water as moving. There are equatorial 
currents or drifts moving westward, one on each side of the equator, 
in both the Atlantic and Pacific oceans. The westward-drifting equa- 
torial waters of the Atlantic are divided at the coast of South America. 
The smaller part is turned to the southwest, and the larger part to the 
northwest, along the border of the continent. Part of the northern 
branch flows through the Caribbean Sea into the Gulf of Mexico, 
whence it issues through the narrow strait between Cuba and Florida 
as the Gulf Stream. This well-defined current is fed partly by the 
water which enters the Gulf from the equatorial drift, and partly by 
that which enters from the land. 

In the Straits of Florida, the Gulf Stream is about 40 miles wide in its nar- 
rowest part, 2,000 to 3,000 feet deep, and has a maximum velocity of about five 
miles per hour. Farther north it becomes wider and slower, until, in the open 
ocean, the rate is perhaps only 10 to 15 miles per day. As it becomes slow, its 
boundaries become less distinct, and it is recognized by its temperature, color, 
and life more readily than by its motion. 

As it advances, the Gulf Stream turns toward the east (to the 
right), crosses the Atlantic, and approaches the coast of Europe in a 
latitude farther north than that where it leaves the coast of America. 
As it approaches Europe, it divides and spreads, but long before 
Europe is reached (about latitude 40 N.), the current has become 
a widespread drift of water, not easily distinguished. This favorable 
current and the westerly winds make the voyage for sailing vessels 
from this country to England much quicker than the return trip. 



iSo 



THE OCEANS 



That part of the equatorial drift which is turned southward along the 
coast of South America soon turns to the left (Fig. 66). 

The equatorial drifts of the Pacific follow courses similar to those 
of the Atlantic. The part which turns north is the Japan Current. 
The Indian Ocean has a south equatorial drift only, and its course 
corresponds to that of the southern part of the equatorial drifts of 
the other oceans. All currents moving toward the poles from the 
equatorial region are warm currents. 

The movement of warm waters into the polar oceans makes a return 
movement necessary. Cold waters moving equatorward from these 
oceans are turned to the right in the northern hemisphere, and to 
the left in the southern. The result is to throw them to the eastern 
coasts of the continents, where in places they form distinct cold 
currents. Along the east coast of North America, the Labrador Cur- 
rent sometimes brings icebergs south to latitude 40 , while in the warmer 
waters of the northeastern Atlantic, drift-ice rarely is encountered 
south of latitude 70 . The Labrador Current chills the air above it, 
and this helps to make northeast winds in New England cold. 

The equatorial drifts are caused and directed by the trade-winds. 
Outside the tropics the winds do not blow in one direction all the 
time, and so do not produce persistent drifts or currents. In regions 
of strong monsoon winds, as about India, the drift of the surface 
waters changes with the wind. 

If the ocean covered all the earth, the westward drift of equatorial 
waters caused by the trade-winds would go round and round the 
earth. But the continents deflect the waters, turning them north 
and south. Once turned in these directions, the waters would tend 
to follow the coasts but for the deflecting influence' of the earth 's 
rotation. Where the sea is so shallow that the moving water touches 
bottom, the topography of the bottom influences the course of move- 
ment. Ocean currents therefore appear to be started chiefly by the 
winds, and to be directed by winds, lands, and the rotation of the 
earth, and, to a less extent, by the topography of the bottom. 

Ocean currents and atmospheric temperatures. Without ocean 
currents, the isotherms over the sea would follow the parallels some- 
what closely, except near the continents (p. 51). Under such 
conditions, the temperature over the ocean in the latitude of 
the British Isles and northward would be io° F. or more lower 
than now (Fig. 65). Ocean currents do not themselves warm or 
cool the land; but the air over a warm current is warmed by 



THE CURRENTS OF THE SEA 



151 




iS2 THE OCEANS 

the water, and is then blown to the land. Even without the 
Gulf Stream, the western coast of Europe would have a milder winter 
climate than the eastern coast of North America in the same latitudes 
(p. 51), but the drift of warm water into the North Atlantic makes 
the winter temperature of Europe north of latitude 50 considerably 
warmer than it would be otherwise. Thus the harbor of Hammer- 
fest, Norway, Lat. 76 , is affected by ice little more than that of 
New York, Lat. 40 . The Japan Current likewise lessens the cold 
of winter on the northwestern coast of North America. 

Warm currents often help to cause fogs, both at sea and on land. 
When wind blows over a warm current, it takes up a large supply 
of moisture. If it then blows over colder water, it is cooled, and some 
of its moisture is condensed, producing a fog. Fogs are common 
along the Gulf Stream, especially where the adjacent land or 
water is much cooler than the current itself. Fogs are more abun- 
dant about Newfoundland than farther south, because the difference 
between the temperature of the Gulf Stream and its surroundings is 
greater there than farther south. 

Tides. Along most coasts the ocean-water rises and falls twice 
every day, or, more exactly, every 24 hours and 52 minutes. The rise 
and fall of the water are the tides. The tide rises for about six hours, 
when it is high or flood tide, and then falls for about six hours, when it 
is low or ebb tide. In most places there is a distinct interval of little 
or no movement (" slack water") when high tide changes toward low, 
and vice versa. The rise and fall amount to several (3 to 6) feet in 
most places. In bays which open broadly to the sea, but are narrow 
at their heads, the range is sometimes 20 or 30 feet, and in rare cases, 
as in the Bay of Fundy (Figs. 67 and 68), 50 feet or more. Where bays 
have a narrow entrance and widen within, the tidal range is small. 
Tides are absent in small lakes, and are feeble in large lakes and in 
seas connected with the ocean by a narrow passage, such as the 
Mediterranean Sea and the Gulf of Mexico. 

In many shallow harbors the tides have an important effect on 
navigation (Figs. 67 and 68). Even some of the most important 
ports depend on the rise of the tide for the movement of their com- 
merce. Thus at Liverpool vessels arriving at low tide must wait, in 
many cases, for high tide, before the water is deep enough for them to 
dock, and vessels must arrange hours of departure to match high tides. 
Where the tide runs in among islands, or passes through narrow 
straits, it causes distinct currents (tidal races), eddies, and whirlpools, 



\ 



TIDES AND COMMERCE 



153 



like the famous Maelstrom near the Lofoten Islands. Sailing vessels 
frequently have serious difficulties with tidal races, as at Hell Gate, 
New York, and in Vineyard and Nantucket sounds, off the coast of 



■^ 






1 



Fig. 67. Low tide at Wolfeville, Bay of Fundy, Nova Scotia, Sept., 1903. 
In March, 1904, the end of the pier was washed away in a storm, and the light- 
house was damaged. (Roland Hayward.) 



Massachusetts. Fishermen commonly speak of the tide as " coming 
in," or " going out," and time their movements to take advantage of 
In many ways tides are more important to navigation than ocean 



it. 



4 JJLT 



Fig. 68. High tide at the same place shown in Fig. 67. (Roland Hayward.) 

currents, and much effort is devoted to charting them for the benefit 
of navigators. 

The tide runs far up many rivers. At Troy, some 150 miles up 
the Hudson River, the range of the tide is more than two feet, and 
tides ascend the St. Lawrence nearly 300 miles. 



154 THE OCEANS 

It is at least two thousand years since the moon was first thought to cause the 
tides, but only about two hundred years since Newton explained how the moon 
produces them. Without attempting to give a full explanation of the tides, some 
of the principles involved may be understood. If a weight is attached to a string 
and whirled, it tends to fly away in a straight line. It is prevented from doing so 
by the string, which holds it in its circular path. The tendency to fly away is what 








Fig. 69. Diagram to show the tendency of the moon to raise the water on 
the side of the earth toward the moon and on the opposite side at the same time, 
producing two high tides. 

is called centrifugal force. The earth and moon attract each other (p. 147), and 
would fall together but for the centrifugal force due to their motions. At the 
center of the earth, and at the center of the moon, the attraction between these 
bodies is exactly balanced by the centrifugal force due to their revolutions. The 
result is that neither falls toward the other. But on the side of the earth nearest 
the moon the attraction is stronger than at the center of the earth (p. 148), and is 
greater than the centrifugal tendency. The attraction of the moon, therefore, tends 
to make the earth bulge out on the side nearest the moon. On the opposite side of the 
earth the attraction is weaker than at the center, and is less than the centrifugal 
force. Here, too, the earth tends to bulge out. The solid part of the earth is so 
rigid that it does not rise enough to be felt or seen. But the waters of the ocean . 





Fig. 70. Diagram to show the relative positions of the earth, moon, and sun, 
at the time of new moon ( = spring tide). Size of moon (M) and earth (E) great- 
ly exaggerated. 

move easily, and rise a little, and the rise takes place on opposite sides of the 
earth at the same time. This makes the. high tides. Between the high tides the 
water sinks a little, making the low tides. The rotation of the earth makes the tides 
appear to move about the earth. 

If all the earth were covered with water, its surface would have two great tidal 
bulges or waves at the same time (Fig. 60). The highest part of one would be a 
point directly under the moon, and the highest point of the other would be opposite 
the first. Each wave would cover half the earth, and the borders of the two would 
meet in a great circle, where the surface of the water would be lowest. 

If the moon were not revolving about the earth, high tide at any place would 
come every 12 hours. But the moon moves forward in its orbit about the earth, 



THE CAUSE OF THE TIDES 155 

so that it takes 24 hours and 5 2 minutes for a given place to have the same relation 
to the moon that it had the day before. This makes the period between successive 
high tides 12 hours and 26 minutes. 

The movements of the tides are not so simple as the outline above would imply. 
Many things interfere. The continents stop or divert the advance of tidal waves, 
and the waves travel more slowly in shallow than in deep water (Why?). Since 
tides are retarded most near land, their advance is here most irregular. For these 
reasons, the time of high tide at most places differs from the time when the moon 





Fig. 71. Diagram to show the relative positions of the earth, moon, and sun, 
at the time of full moon (= spring tide). 

crosses their respective meridians. This difference in the time of arrival of high 
or low tide may be determined for any harbor, and is called the " establishment of 
the port." At New York, for example, high water arrives 8 hours and 13 minutes 
after the moon passes the meridian. Tables showing the "establishment" of 
different ports are of great value to navigators. 

The sun also attracts the earth, and tends to cause tides. If there were no moon 
there would still be small tides produced by the sun. The tides which we know 





Fig. 72. Diagram showing the tendency of the sun and moon to produce 
tides on opposite parts of the earth at the time half way between new moon and 
full moon, and half way between full moon and new moon. 

are the combined effects of moon and sun, but the moon's tides are much the 
stronger. The sun strengthens the tides when sun and moon work together, and 
weakens them when they work against each other. 

When sun and moon stand in the relation to each other and to the earth shown 
in Fig. 70 (new moon), each tends to make high tides at A and at B. When the 
relations are those shown in Fig. 71 (full moon), the result is the same. At these 
times, and each occurs once a month, high tides are higher, and low tides lower, 
than at other times. The tides of such times are called spring tides. They have 
no relation to the spring season. 

When the earth, moon, and sun have the relative positions shown in Fig. 72, 
and this occurs twice each month, the tidal influences of the sun and the moon are 



1 56 THE OCEANS 

opposed to each other, and the result is that high tides are not so high, nor low 
tides so low, as under other conditions. The tides of such times are known as 
neap tides. Spring tides have nearly twice the range of neap tides in many places. 

In the open ocean and along precipitous coasts, the tide is like 
other waves, merely a rising and falling of the water. Like other 
waves also, the water of the tidal wave moves forward when it ap- 
proaches shores where the water is shallow. 

In shallow waters near the coast, tides alternately cover and 
expose wide expanses of sandy beach or mud flats, as the case may 
be. The water-line at low tide may be a quarter of a mile or more 
from its position at high tide. Tidal currents may be effective agents 
of erosion, maintaining deep channels in harbors, to the great ad- 
vantage of commerce. By the circulation they cause, tides in 
some cases help to remove filth which otherwise would accumulate in 
harbors. Sewage disposal is always easier for cities near tide-water. 
On the other hand, the sediment drifted about by tides may be de- 
posited in harbors. This makes expensive dredging necessary, in 
order to maintain a sufficient depth of water for shipping. The 
frequent shifting of the deposits renders it impossible to indicate the 
channel on the pilot charts of some harbors. 

The large volume of water rising and falling in tides has led to 
many attempts to develop tidal water power. Small tide-mills are 
used for grinding grain and other purposes at various places in western 
Europe, and a few larger power plants have proved useful, as in the 
Seine estuary. 

The Life of the Sea 

Animals and plants abound at and near the surface of the sea, 
and at the bottom where the water is shallow. A bucket of water 
dipped up from the surface of the ocean almost anywhere will con- 
tain hundreds or even thousands of minute plants and animals, though 
most of them are too small to be seen without a microscope. Liv- 
ing things are present, but not in great numbers, at the bottom of 
the deep sea; but in the water between the uppermost ioo fathoms 
and the bottom, there is little life. 

The temperature, the depth, the clearness, the saltness, and the 
quietness or roughness of the water, influence the life which it con- 
tains, in ways easily understood. The depth of the water has little 
or no effect on plants and animals which float or swim near the sur- 
face; but at great depths the supply of oxygen is slight, and there 



THE LIFE OF THE SEA 157 

is not light enough so that animals can see much below 50 fathoms. 
In the great body of the ocean darkness reigns, and green plants, 
which depend directly on sunlight, cannot live in darkness. 

Though the pressure of the water at the bottom of the ocean is 
very great (p. 143), the animals living there can stand it because their 
bodies are full of liquids under the same pressure, and these great 
pressures within their bodies balance the great pressures without. 
If an animal from the bottom of the deep sea were brought suddenly 
to the surface it would explode (Why?). Even when raised slowly, 
they sometimes explode as they near the surface. 

Some animals, such as the polyps which make coral, live only in 
warm regions. Others, such as narwhals and seals, are found only 
in cold waters. Still others are found in both warm and cold waters. 
The unequal distribution of ocean temperatures by warm and cold 
currents influences greatly the character of marine life in different 
parts of the sea. 

In many ways the life of the sea is in strong contrast with that of 
the land. Thus most familiar land plants are fixed in position, but 
many sea plants float. Most land animals are free to move about, 
while many of those in the sea, such as polyps and barnacles, are 
fixed through most of their lives. Many which are not fixed move 
about but little, either lying on the bottom or burrowing into it. 
Some, on the other hand, as many of those in the surface waters, 
appear to be moving always. 

All the great groups of animal life are represented in the sea. 
Even warm-blooded mammals (whales, seals, walruses, etc.) abound 
in frigid waters, among icebergs and ice-floes. Some of them, like 
the seals and walruses, do not spend all their time in the water, but 
frequently crawl up on the ice or land. 

Not only are there many varieties of marine plants and animals, 
but the largest modern animals (whales) live in the sea. Many sea 
plants, too, are of great size. Some sea-weeds are six inches in diam- 
eter, and some have a length greater than that of the tallest trees. 

The total value of food products — fish, oysters, clams, crabs, lob- 
sters, etc. — derived from the sea probably is not less than $500,000,- 
000 per year. The best fishing regions are found where large areas of 
shallow water, as over broad continental shelves, furnish extensive 
feeding and breeding grounds for vast numbers of fish. The most 
important region of this sort is the area of shallow water about the 
British Isles, including the North Sea. The British fisheries employ 



158 



THE OCEANS 



more than 100,000 men, and yield an annual catch valued at more 
than $50,000,000. Similar conditions led to the development of im- 
portant fisheries from New England (p. 375). 

Other sea animals furnish other articles of commerce. The seal 
furnishes fur and oil; the whale, oil and whalebone; and the hide of 
the walrus makes exceptionally strong leather. Coral and sponges, 
products of animal life, are also articles of commerce. Sea-weed was 




Fig. 73. Coral formations, Samoa. (Muir and Moodie.) 



used formerly as the chief source of soda and of iodine. Some varieties 
still are gathered in large quantities on the coast of Massachusetts 
and Europe, to be used as food under the name of " Irish moss." 

Coral reefs. The little polyps (Fig. 73) which secrete coral 
live where the water (1) is 120 feet or less in depth, (2) is never colder 
than about 68° F., (3) has the saltness of normal sea- water, (4) is 
free or nearly free from sediment, and (5) is subject to some movement 
by the wind. Where these conditions exist, polyps thrive and make 
reefs, and the reefs may become islands. Polyps flourish along the 
borders of many tropical lands, and in some places far from shore. 

Coral reefs are of several classes. Those which are separated from 
the land by a somewhat deep channel or lagoon are barrier reefs. 
Those close to the land are fringing reefs. Rudely circular reefs 



CORAL REEFS AND ISLANDS 159 

inclosing a central lagoon are atolls. The chief importance of coral 
reefs is their relation to navigation. Atolls frequently afford shelter 
to vessels in distress. Submerged reefs, however, are dangerous, and 
long barrier reefs may hamper commerce seriously, as along the east 
coast of Australia. 

The use of pink or red coral for jewelry leads to important coral 
" fishing" in the Mediterranean, whence much of the product goes to 
India. Most of the natives of coral islands are backward in civiliza- 
tion, because of the limitation of their resources. 



Questions 

1. Why is agriculture possible on a limited scale in Alaska, and not in the 
same latitudes in Labrador, Greenland, and Baffin Land? 

2. Why is Alaska less favorable for agriculture than Norway? 

3. Why is the climate in latitude 50 , on the west coast of South America, 
less favorable for farming than that in latitude 50 on the west coast of North 
America? 

4. Why are isotherms (Fig. 65) affected less by ocean currents in the 
southern hemisphere than in the northern? 

5. Why is the water along the equator in the Pacific Ocean warmer toward 
the western border of the ocean? What does the principle involved suggest in 
regard to the surface temperatures in the Gulf of Mexico? 

6. Why are steamer routes across the Atlantic farther south in summer 
than in winter? 

7. In order to enter a shallow harbor, is a vessel more likely to have to wait 
for flood tide at the time of neap tides or at the time of spring tides? Why? 

8. On which side of the Gulf Stream, in latitude 45 , are fogs more com- 
mon? Why? 

9. Are fogs more likely to occur over a warm current, or over a cold one? 
Why? 

10. What inference might be drawn from the fact that polyps once lived within 
the Arctic Circle? 

n. What changes in geography are implied by the fact that polyps once lived 
in eastern Wisconsin? 



CHAPTER XIII 
THE MATERIALS OF THE LAND AND THEIR USES 

General Constitution 

The mantle rock. The loose material such as soil, clay, sand, and 
gravel, which covers most of the land, is called mantle rock, because 
it forms a mantle over the solid rock beneath. Mantle rock varies 
in thickness from a few inches to scores or even hundreds of feet. 
It is formed by the decay and breaking up of solid rock, and for this 
reason is called also rock waste. 

Soil is the uppermost part of the mantle rock, which serves as a 
source of food for plants. It varies in thickness from two or three 
inches to as many feet, and locally, much more. Soil consists of small 
particles of minerals, usually mixed with partly decayed vegetable 
matter {humus) . Both mineral and organic matter are necessary parts 
of a good soil, but their proportions vary greatly. In color, soil may 
be yellow, dull red, gray, brown, or, when much humus is present, 
black. It may be either clayey and compact, or sandy and porous. 

In order to support plant life, soil must contain both air and water. 
Air always is present in sufficient amount, unless crowded out by 
excess of water, as in some swamp soils. On the other hand, the 
necessary amount of water may be lacking, as in deserts. Such soils 
are barren, even though perfect from the physical and chemical stand- 
points. In western United States, large areas of barren land need 
only water to be of great value. 

In excavations, as for cellars, wells, railway cuts, and the like, 
soil may be seen to grade down, in many places, into subsoil, which 
is different in color and texture from the soil above. In most places 
the subsoil is much thicker than the soil, though it may be absent 
altogether. 

Solid rock. Beneath the subsoil is solid rock (Fig. 74). This 
extends down to great depths, probably even to the center of the 
earth. In interior United States, solid rocks may be seen chiefly 
in quarries, mines, along the courses of certain rivers, and in a few 

160 



THE SOIL A FUNDAMENTAL RESOURCE 161 

other situations; but in eastern Canada, in western Scandinavia, 
among high mountains generally, and in many other places, they 
come to the surface over large areas. Such places have little value 
from the standpoint of agriculture, even though other conditions are 
favorable. 

Soils 

Importance to man. Man, depends, directly or indirectly, on 
soil for most of that which he eats and wears. Products of the soil 
furnish the principal articles of commerce, and its cultivation con- 




Fig. 74. Diagram showing soil grading into solid rock beneath. 

stitutes the chief basis of civilization. These relations, too, are last- 
ing ones. Whether the United States shall in the future support a 
numerous, well-to-do, progressive population, or a sparse, under-fed, 
and non-progressive one, is largely a question of whether the soil of 
the country is kept abundant and fertile. In 1900, more than a 
third of the wage earners of the United States were employed in 
farming. 

The Making of Soils 

We have seen that most soils are formed by the decay and break- 
ing up of solid rocks. All changes which make solid rock crumble are 
processes of weathering. The weathering of rock prepares it for 
transportation by wind and water. 

Chemical processes. The oxygen, carbon dioxide, and water 
vapor of the air are active chemically. The meaning of chemical 



l62 



MATERIALS OF THE LAND — THEIR USES 



action is illustrated by the rusting of iron. Iron rust is composed 
of iron, oxygen, and water. Oxygen and water from the air enter 
into chemical combination with the iron. While all three of these 
substances are in the rust, the rust does not look like any one of them. 
The union of oxygen with any other substance, as iron, is oxidation. 
The union of water with another substance is hydration. Iron rust 
is therefore oxidized and hydrated iron. 

If rusting is allowed to continue, iron is, in time, "eaten away"; 
that is, it crumbles to pieces. In this case, as in many others, chemical 
change produces physical change. Many rocks contain iron which 
may be oxidized and hydrated. When such rocks are exposed to 
the air, therefore, the iron in them is changed (rusted), and this tends to 
make the rock crumble. Other chemical changes tend to produce the 
same result. Some of the substances made by chemical changes in the 
rocks are soluble, and if they are dissolved and carried away by 
waters passing through the rock, the rock from which they are taken 
is left more porous, and weaker. Some rock-making minerals are 
soluble without chemical change, so that solution is one of the most 

important means by 
which rocks are made 
to crumble, and by 
which soils are formed. 
Mechanical proc- 
esses, (i) When 
water freezes, it ex- 
pands about one-tenth 
of its volume, and in 
doing so exerts great 
force. When it freezes 
in rock cavities which 
it nearly fills, it acts 
like a wedge, and may 
pry the rock apart and 
break off pieces. This 
process of rock-break- 
ing is most important 
when there is abundant moisture, and where the changes of 
temperature above and below the freezing point of water are fre- 
quent. Rock-breaking is a first step in the making of soil from 
rock. 




Fig. 75. Surface of bowlder scaling off under 
changes in temperature. (Taff, U. S. Geol. Surv.) 



HOW SOIL IS FORMED 



163 



(2) Where solid rock has no covering of loose material, as on many 
steep slopes, it is heated by day and cooled by night, and the daily 
changes of temperature 
may be great. Rocks ex- 
pand when heated and 
contract when cooled, and 
under daily heating and 
cooling their surface parts 
break and scale off (Fig. 
75). The breaking of cold 
glass when touched with 
hot water, or of hot glass 
when touched with cold 
water, involves the same 
principle. The shattering 
of rock by heating and 
cooling is very common, 
particularly in high moun- 
tains. Thus the upper 
part of many a mountain is covered with broken rock (Fig. 76), so 
insecure that a step may loosen many pieces and start them down the 
mountain. Great piles of such debris (called talus) bury the bases 



r 


HP"^ 


1 


"*! m 


■ : ;+< 


1 


' ' 1 

L" ft 




1 

V:*^ 



Fig. 76. Summit of Granite Peak, Wa- 
satch Mountains, showing broken character 
of the rock. (Church.) 




Fig. 77. View showing long talus slopes. (Russell, U. S. Geol. Surv.) 



i6 4 MATERIALS OF THE LAND— THEIR USES 




of some mountains to the depth of hundreds of feet (Fig. 77). This 
debris tends to decay, gradually forming soil, after which, if other 
conditions are favorable, the slope is occupied by plant life. 

(3) The growth of roots in cracks in the rocks may enlarge the 
openings, and so help to break the rocks (Fig. 78). 

(4) The multitudes of burrowing animals make openings in the 
ground, and bring large quantities of loose material to the surface, 

where it is exposed to air and 
water, and is by them changed to 
soil. 

(5) Rivers wear the bottoms 
and sides of their channels, and so 
help reduce solid rocks to fine 
material. 

(6) Glaciers grind and crush 
masses of rock into such fine mate- 
rial that some of it is called "rock 
flour." Much of the mantle rock 
of northeastern United States 
was ground up by ancient glaciers 

(p. 2 5i). 

(7) In many dry regions, wind- 
driven sand wears exposed rocks and forms much fine, loose material, 
capable of becoming soil. 

Classes of Soils 

In the paragraphs which follow, the term soil is used to include 
the subsoil also, where the distinction between them is not important. 

Soil which remains above the solid rock from which it was formed 
is residual soil (Fig. 74). On the other hand, transported soil has 
been brought from its place of origin to its present position by some 
of the agents (wind, water, or ice) which transport materials on the 
surface of the earth. In general, transported soils are richer than 
residual soils, though this is not always the case. 

Residual soils. All kinds of rock decay, and the decayed rock, 
properly weathered, becomes soil. Residual soils vary greatly in 
fertility, much depending on the character of the parent rocks. 
Thus most sandstones weather into poor soil. Shales produce clay soils 
of greater average fertility, but in some cases they are heavy, and hard 
to work. Limestone soils are, as a class, very fertile, but if their 



Fig. 78. A tree growing in a 
crack in the rock. The growth of 
the tree widens the crack. Sierra 
Nevada Mountains, California. 



CLASSES OF SOILS 165 

limey constituents are dissolved out, as they may be, the soil is less 
fertile. 

Transported soils. Transported soils are much less uniform in 
composition and texture than residual soils. In many cases they 
represent material gathered from a large area, and are entirely unlike 
the rocks on which they rest. Sediment transported and deposited 
by rivers is alluvium, and soils formed on alluvium are alluvial soils. 
Such soils in the flood-plains and deltas of great rivers, when not 
too wet, are commonly of great fertility. The rich soil of the great 
alluvial fan (p. 235) of the Hwang-ho, in China, supports one of 
the densest populations in the world. Ancient civilizations were 
confined so generally to rich flood-plain soils that the period before 
800 b. c. has been called the Fluvial Period. 

Eolian soils are formed from sand or silt deposited by the wind. 
Eolian deposits cover large areas in various regions (p. 202). While 
the sand is loose, and being blown about, it is hardly soil and offers 
little chance for agriculture. For this reason, part of an extensive 
area of sand-hills in western Nebraska has been set aside for a National 
Forest. It is believed that certain trees which can get along with 
little moisture may be grown there, and that the entire sand area, 
now almost worthless, may be covered with a profitable forest. 
Large areas of land have been reclaimed in this way in southwestern 
France. 

Wind has deposited loess in certain regions. Loess is a loam, of 
buff or gray color, coarser than clay, and finer than sand. Soils 
formed from loess are very fertile when well watered. Some of the 
best farming lands of the Rhine, Danube, and other European river 
basins have loess soils. Similar soils occur in some parts of the 
Mississippi Basin, particularly along parts of the Mississippi and 
Missouri rivers. 

Before the Civil War, the counties of Missouri covered with loess contained a 
larger percentage of slaves than most of the rest, and grew large quantities of 
tobacco. The loess-covered counties of eastern and southeastern Nebraska 
produce most of the corn, wheat, oats, and alfalfa grown in the state. They are 
settled more thickly, and have more improvements, than most of the rest of the 
state. 

Much of the mantle rock of Canada and northern United States 
was brought to its present position by the great ice-sheets which once 
covered the region (p. 251). This material is called drift. Soil 
formed from drift varies much in character and fertility. Some of 



i66 



MATERIALS OF THE LAND — THEIR USES 



it is too sandy and some is too stony to be farmed with success, but 
much of it is of excellent quality. Since the glacial drift was made 
not very long ago (as geology reckons time) by the grinding up of 
rocks of many kinds, the soils made from it are likely to contain all 
the mineral elements needed for plant food. 

The Removal of Soils 
Relation of gain and loss. It has been estimated that in the 
United States it may take, on the average, 10,000 years to form a 
foot of residual soil (833 years for an inch). Slow as this rate is, it is 
faster than the average rate at which soil is removed by surface 
waters, winds, etc. If soil were removed faster than it is formed, the 
land would in time be without soil, as it is now in some places, espe- 




Fig. 79. View in the Apennine Mountains, near Florence. Shows the shall 
low, stony soil which remains after the loam has been washed away. By removing 
the slight protective cover of vegetation, the sheep promote further erosion. 
(Sketch from photograph by Willis.) 



daily on steep slopes. With the clearing away of forests and the 
plowing of land for agriculture, the rate of soil erosion was increased 
greatly, and it now exceeds the rate of soil formation over large areas. 
From parts of the Apennine Mountains (Fig. 79), Dalmatia, Pales- 
tine, and China (Fig. 80), where the land was cultivated for centuries, 
the soil has been washed away, and the land is now barren. This 
shows what must be expected in some parts of this country, if the 
washing away of soil is not checked. The Mississippi River carries, 



LOSSES FROM SOIL EROSION 



167 



on the average, more than 1,000,000 tons of the richest soil matter 
into the Gulf of Mexico every day. The work performed each year 
by the Missouri River in transporting material toward the sea is 
estimated to be equivalent to 275,000,000,000 ton-miles (a ton-mile 
is a ton carried a mile). All the railroads of the United States carried 
800,000,000 ton-miles of freight in 1909. The annual loss to the 



21 



country from the washing and leaching of soil is estimated at some 




Fig. 80. View in the western part of the province of Chi-li, China. The 
erosion has been aided in places by recent deforestation. (Willis, Carnegie Insti- 
tution.) 



$500,000,000. Although the land, even of eastern United States, 
has been cultivated but a short time compared with that of Europe, 
yet nearly 11,000,000 acres once farmed have been abandoned. More 
than one-third of this area has been ruined for farming by the erosion 
of the soil. It has been estimated that the area thus ruined would, 
if covered by fertile soil, be capable of supporting a population greater 
than that of any one of the twelve least populous states. Doubtless 
the total loss to the country from the partial destruction of soil is 
even greater. Nor is this all. (1) The soil carried away may do much 
harm where it is deposited. (2) Streams which carry much sediment 
deposit some of it in their channels, thus interfering with navigation. 
(3) The clogging of river channels also helps to cause floods. (4) Res- 



168 MATERIALS OF THE LAND — THEIR USES 



ervoirs, such as mill-ponds, may be filled with sediment, interfering 
with manufacturing. (5) Streams are polluted, interfering seriously 
with their use as a source of water supply for cities, and making- 
expensive filtering plants necessary. 

Factors controlling soil erosion. Several factors influence the 
rate of soil erosion. (1) It is greater on steep slopes than on gentle 
ones. Lands in the southern Appalachians have been cleared of 
forests and cultivated where slopes are so steep that the soil was 

washed away in eight 
or ten years, and the 
land abandoned. (2) 
It varies with the 
amount and distribu- 
tion of rainfall. The 
more the rainfall and 
the more rapidly it 
falls, the more rapid 
the erosion of the soil. 
The greatest storm of 
a year may wash away 
more soil than all the 
other rains of that 
year. (3) It is influ- 
enced by the presence or absence of vegetation, and in the case of 
cultivated land by the kind of crop. Bare soils, and those devoted 
to widely-spaced plants, wash faster than grass lands and forest 
lands. (4) It is affected by the texture of the mantle rock and 
solid rock. (Which would favor greater wash, compact or porous 
soil? Compact or porous material below the soil?) 

Prevention of soil erosion. There are various ways of reducing 
soil erosion. The more important are the following: (1) Deep and 
frequent tillage increases the power of the soil to absorb rain, and 
so reduces the amount of water running directly off over the surface. 
This is highly desirable apart from its effect on erosion, for few 
places have water enough to produce maximum crops. (2) Plowing 
and planting along contours (p. 16) produce little depressions and 
ridges at right angles to the slope. These tend to check erosion 
(How?). Plowing up and down a slope, on the other hand, increases 
erosion (Why?). (3) On steep slopes, wash may be reduced by making- 
a series of terraces or benches. Terracing is practiced in parts of the 




Fig. 81. Terracing in western North Carolina. 
(Sketch from photograph by N. C. Geol. Surv.) 



MINERAL PLANT FOODS 



169 




Piedmont Plateau (Fig. 81) and elsewhere in the South, and in many 
countries of Europe and Asia (p. 312). (4) The soil should be kept 
covered with vegetation as much as possible throughout the year. 
(5) Grasses tend to prevent wash in several ways (How?). (6) On 
slopes exceeding 18 or 20 in steepness, the soil is protected best 
by trees (Fig. 82), and, in general, such land should be devoted to 
forests. Lessening soil 
erosion is one of the 
most important prob- 
lems of conservation, 
and it depends very 
largely on individual 
land-owners. 

Mineral Plant Foods 
Proper care of the 
soil calls for (1) the 
prevention of erosion 
so far as possible, and 
(2) the keeping in the 
soil of the mineral mat- 
ters needful for plant 
food. The mineral sub- 
stances of importance 

are phosphorus, potassium, calcium, and silicon, though a few others 
are used in small quantities. Besides these mineral substances, plants 
need carbon, hydrogen, oxygen, and nitrogen. Different crops draw 
unequally on the mineral foods of the soil, and when one crop is grown 
on the same ground year after year, the soil may become poor in one 
or more of these foods, and its productivity be reduced. The almost 
exclusive cultivation of tobacco injured the soil in parts of colonial 
Virginia. This helped to send thousands of farmers west of the 
Appalachian Mountains in search of new land. Southern Wisconsin 
was primarily a wheat region from the 1830's to the 1870's, when 
the diminishing yields and the competition of the new, rich soils 
farther northwest led to the raising of other crops, and the adoption 
of better methods of farming. Where crops of different kinds are 
raised, one after another (rotation of crops), the soil remains in 
better condition; but unless the essential elements taken from the 
soil by plants are returned in some way, its fertility must diminish. 



Fig. 82. View showing effect of roots in hold- 
ing soil. San Juan Mountains, Colorado, near 
Silverton. (Fairbanks.) 



170 MATERIALS OF THE LAND — THEIR USES 

" Worn-out" farms are common in the South and East, and even in 
parts of the Upper Mississippi Basin. Land may be kept from 
wearing out by giving it the elements it lacks, that is by fertilizing 
it. In some parts of the southeastern states, where the soil was 
made poor by the long-continued growth of cotton or tobacco, no 
crops are grown without the use of fertilizers. 

Natural processes tend to add to the soil the substances essential to plants. 
New soil is formed by the weathering of underlying rocks (p. 161), and ground- 
waters bring mineral matter in solution from below, which they may deposit near 
the surface, enriching the soil. In most cases, these processes of soil renewal and 
enrichment fail to balance the loss which results from the common methods of 
farming. While certain natural processes tend to enrich soils, surface and under- 
ground waters may also erode and leach them (p. 211), thereby reducing their pro- 
ductivity. 

The supplies of most of the elements which plants need are 
abundant in the air, the ground- water, or the soil. Hydrogen and 
oxygen are the constituents of water, and oxygen makes one-fifth 
of the atmosphere. The air contains an unlimited supply of nitrogen, 
but most plants get their nitrogen from compounds of that substance 
in the soil or in fertilizers (p. 29). Next to oxygen, silicon is the most 
abundant element in the earth's crust. Most rocks contain a little 
calcium, and limestone contains much. Carbon is derived from the 
carbon dioxide of the air. Potassium is a constituent of many common 
rocks, and there are large deposits of potassium compounds in various 
places. Wood ashes contain potassium, and for this reason they are 
good for land. 

Unlike the foregoing, phosphorus is a relatively rare element, and 
already the original amount in the soil has been diminished seriously 
in many parts of the United States. Guano, chiefly from islands off 
the west coast of South America, is an important source of supply, 
though little is imported into the United States. The bones of do- 
mestic animals are a second source, and the manufacture of phosphate 
fertilizer is an important industry at the great slaughtering centers. 
The bones of buffaloes, killed in great numbers years ago, have been 
gathered up by the train-load from the western plains and used in the 
same way. Enormous quantities of phosphorus are now lost in the 
sewage of great cities, and in the leaching of farm manure. This 
phosphorus should be returned to the soil, so far as possible. Some 
European countries are far ahead of the United States in this matter. 
Finally, the United States possesses the greatest known deposits of 
phosphate rock (rock containing much phosphorus), and because 



DISTRIBUTION OF SOILS IN UNITED STATES 171 

phosphorus is to be a critical factor in the fertility of soil, these de- 
posits constitute one of the most important mineral possessions of the 
nation. In the Southeast, there are deposits in South Carolina, Flor- 
ida, Tennessee, and Arkansas. The first three of these states furnish 
nearly all the phosphate rock now mined in the United States. In 
addition, there are far greater deposits in Idaho, Wyoming, Utah, 
and Montana. There is, unfortunately, much waste of the poorer 
phosphate rock in mining — material which, if saved, would be of 
great value in the future. Unfortunately for the United States, too, 
increasingly large amounts of phosphate are being exported. 

It is not to be inferred from the above discussion that fertility of soil is deter- 
mined solely by its chemical composition. Its productivity is influenced also by 
(1) its physical condition (coarseness, fineness, etc.), (2) its water content, (3) the 
organic matter (humus, etc.) which it contains, (4) the minute organisms (especially 
bacteria) at work in it, (5) the presence of toxic bodies (the accumulated excreta of 
plants) , and by other factors. Furthermore, the yields obtained from a given soil 
are affected greatly by (1) the quality of seed sown, (2) the effectiveness of cultiva- 
tion, and, in many cases, by such things as (3) harmful insects, (4) plant diseases, 
and (5) weather conditions. The reduced yields of many long-cropped soils 
probably are due in part to causes other than the impoverishment of the mineral 
elements of plant food. 

General Distribution and Use of Soils in the United States 

The principal physiographic provinces of the United States are shown in Fig. 
83. Since the settlement and development of these provinces have been influenced 
profoundly by the topography of the land and the character of the soil, the larger 
provinces may be considered briefly. 

The Atlantic and Gulf Coastal Plains. Much of the Coastal Plain is less than 
100 feet above sea-level, though some parts of it are considerably higher. The 
underlying rocks are imperfectly cemented gravels, sands, clays, marls, and lime- 
stones. Along the coast there are extensive marshes, where most of the soil is too 
wet to cultivate. The draining of these swamps has been begun, as for example 
on the delta and lower flood-plain of the Mississippi, and when it is completed their 
rich soils will support many people (p. 301). Elsewhere, the soils of the Coastal 
Plain present great variety. Over the marls and limestones they are fertile, and 
over the sands, gravels, and clays, they are much less productive. Many sandy 
tracts, as in parts of southern New Jersey, have remained wooded and sparsely 
settled to the present. In the Carolinas such belts, called "barrens," long helped 
to separate the life of the tidewater country from that of the Piedmont Plateau. 
In contrast with the sandy areas, the bottom lands of the rivers, where not too wet, 
and the belts of limestone soils are the garden spots of the South. Here most 
cotton was grown before the Civil War, and most slaves were owned (p. 325). 
Here the negro population is densest to-day. It probably is true that the rich soils 
of many parts of the Coastal Plain, and the genial climate of the South, were re- 
sponsible for the continuance of slavery in the United States to the time of the 
Civil War. 



172 



MATERIALS OF THE LAND — THEIR USES 



The New England Hills. There is no continuous coastal plain in New 
England. The most important lowlands have developed on weak rocks in the 
Connecticut Valley, about Narragansett Bay, and around Boston. On these low- 
lands the early history of Connecticut, Rhode Island, and Massachusetts centered. 
To-day, the Boston Basin contains about half the people of Massachusetts, and 
one-fourth those of all New England. Apart from these lowlands, most of New 
England is hilly. Much of its glacial soil is thin and poor, and in many places 
stony. It has been estimated that in some parts it took, on the average, one 
month for a man to remove the stones from each acre of glacial drift, to get it ready 




Fig. 83. 
States. 



Map showing the principal physiographic subdivisions of the United 



for farming. Many of the early settlements were made in areas of stratified drift 
(p. 266), where the bowlders were fewer and the land flatter. 

The unfavorable soils and the harsh climate prevented a high development 
of agriculture in New England, which was without a single staple crop for export, 
such as colonial Virginia had in tobacco, and South Carolina in rice and indigo. 
By the close of the seventeenth century, more than half the people of New England 
were engaged in industries other than agriculture, and it is said also that more than 
half the time of the farmers was given to non-agricultural work. For two centuries 
the life of New England was dominated by industries centering in the ocean — 
chiefly fishing, shipbuilding, and the carrying trade. Later, manufacturing became 
the leading interest. 

Crude methods of agriculture in early days led to the exhaustion or partial 
exhaustion of many lands which were originally good for farming. When the lands 
(eased to produce good crops they were deserted. Much has been written and said 
of the abandoned farms of New England, but in recent years many of them have 
been brought under cultivation again, and with the improved methods of to-day 
they are producing satisfactory returns. It seems certain that many of the 



DISTRIBUTION OF SOILS IN UNITED STATES 173 

abandoned farms will be reclaimed. Much of the rough, infertile upland, however, 
probably can be used to best advantage in the future for forests. 

The Piedmont Plateau. The Piedmont Plateau has an elevation varying 
from 250 or 300 feet at its eastern edge, to about 1,000 feet in places along its 
western margin. The higher lands have a rather poor, residual soil, but many of 
the valleys have rich, alluvial bottoms. 

The Appalachian Mountains. The soils of the larger valleys are fairly fertile. 
This was strikingly true, originally, of the limestone soils of the Great Appalachian 
Valley, which, under various names, extends from Georgia to New York. This 
great valley was one of the first areas west of the Blue Ridge to be settled, and it 
soon became an important grain producing section. During the Civil War, the 
Confederate armies drew large quantities of supplies from its fertile fields. 

The upper slopes of these mountains are steep, and covered with soil which 
washes easily when the forest is removed. A National Forest is to be established 
in the southern Appalachians, and the steeper land devoted permanently to forestry. 
In the future, the country must look to Appalachian forests for much of its supply 
of hardwood. 

The Cumberland-Alleghany Plateau. The surface of this plateau is much 
dissected by valleys cut in the nearly horizontal layers of rocks. In general, 
relatively level land and fertile soil are found only in the valley bottoms. The hills 
have steep slopes, and their soils are infertile. Except where mineral resources 
have attracted settlers, the plateau is sparsely settled. 

Lake and Prairie Plains. Most of the surface of this area is covered with 
glacial soil (Fig. 170), the composition of which is influenced greatly by the nature 
of the underlying rocks. Thus in Michigan and Wisconsin there are large areas 
of sandy drift over sandstone, where attempts at farming, following the removal of 
the pine forests, have met with little success. There are also hilly belts {moraines, 
p. 258) in the northern part of the area, where the stony soil is used largely for wood- 
lots and pasturage. There is also much marsh land, unfit for agriculture until 
drained. In general, however, the soils of this region, especially the prairie soils 
between the Missouri and Ohio rivers on the south and southwest and the Great 
Lakes on the north, are of great fertility. No other equal area in the United States 
is so important agriculturally (Fig. 257). Iowa, Illinois, Ohio, and Indiana, in the 
order named, are the first four states in the percentage of improved land to total area. 

The prairies generally were avoided by the first settlers, who regarded the 
absence of trees as evidence of poor soil. Even after their fertility was known, the 
larger prairies were not settled far back from the main streams until the building 
of railroads provided means of transportation. 

The Great Plains. The surface of this province rises from an elevation of 
about 1,000 feet at the east, to more than 5,000 feet at the west. Most of the 
region has a deep and rich soil. At the north, the soil is of glacial origin (Fig. 170) ; 
farther south it is (1) partly alluvial, having been spread widely by depositing rivers 
flowing eastward from the Rocky Mountains, (2) partly residual, and (3) consider- 
able areas in the eastern part of the tract are covered with loess (p. 165). The 
eastern part of the area is very productive, but the western part has too little rain 
for ordinary farming. Here agriculture must depend on (1) irrigation, which is 
possible over small areas, (2) "dry farming" (p. 329), and (3) the cultivation of 
drought-resisting plants, such as durum wheat and kaffir corn. Over large areas 
grazing probably will continue to be the chief interest (p. 329). 



174 



MATERIALS OF THE LAND — THEIR USES 



The Rocky Mountains and Western Plateaus. In the different parts of 
this great region all kinds of rocks are found, in all sorts of positions. The soils 
vary as greatly as the rocks, both in origin and composition. Glacial soils are found 
at the north, and throughout the region in many mountain valleys. Great areas 




Fig. 84. Map showing the best use to which it is thought the land through- 
out North America may be put. (Zon, U. S. Forest Service.) 



BUILDING STONES AND CLAYS 175 

of alluvial soil fringe the bases of many of the mountains, where withering streams 
from the uplands have deposited their sediment. Some of these deposits have a 
thickness of hundreds and even thousands of feet. The steep slopes are flanked 
also by great piles of talus (p. 163), most of which do not support much plant life. 
Where the mountain slopes are not too steep, there are residual soils, and these 
also cover great areas of the plateaus. 

Over most of the region, systematic tillage of the soil has not been possible 
because of (1) too great height, (2) the steepness of the slopes, or (3) lack of ade- 
quate rain. Most of the land is therefore best suited to grazing, and, especially in 
the mountains, to forestry. Irrigation is making agriculture possible in many 
rather small areas (p. 293), especially in valleys and on other lowlands. In some 
such places, there is a dense population. Nowhere else in the world is fruit-raising 
carried on more intelligently or with better results, and probably nowhere else in 
the world has farm land sold at such high prices. Small, choice orchards have been 
sold at $4,000 and $5,000 per acre, and prices half as high are not rare. 

The Pacific Ranges. As farther east, the soils of the mountain slopes can 
be used best for forests, for which, except at the south, there is enough rain. Among 
the mountains there are many fertile valleys with glacial or alluvial soils, and 
between the ranges are the great waste-filled valleys of the Willamette River and of 
central California. The rich, alluvial soils of the latter probably have given the 
state larger returns than its gold mines. In the southern part of the province, the 
value of even the best soil depends on irrigation, and unfortunately there is water 
enough to irrigate only about one-tenth of the land. Irrigated land, with groves 
of oranges or lemons, sells for very high prices, while non-irrigable land is worth 
but little. Toward the north, with increase of rainfall and with lower tempera- 
tures, the necessity of irrigation is less. 

Fig. 84 shows, in a general way, the best use to which it is thought the land 
throughout North America may be put, and serves to illustrate many of the larger 
points stated in the preceding paragraphs. 



Mineral Products and Their Uses 
Building Stones and Clay 

Building stones. The principal building stones are granite, 
limestone, marble, slate, and sandstone, though not all rocks of these 
kinds are useful for building. The strength of the rock, its color, ease 
of splitting and dressing, and durability all enter into the problem. 
Not all good stone is available, for much is too far from a market. 
Cement is taking the place of building stone to a very large extent. 

Granite is distributed widely in the United States, and is quarried 
in a large way in several of the Atlantic States. Limestone is quarried 
in many states, largely for local use. From a few famous quarries, 
such as those at Bedford, Indiana, it is shipped to all parts of the 
United States. Much limestone is burned for lime, and much is 
used for mortar, cement, railroad ballast, etc. The growth of the 



176 MATERIALS OF THE LAND — THEIR USES 

cement industry has been remarkably rapid. In 1890, the United 
States produced less than 350,000 barrels of Portland cement; in 
1911, more than 79,500,000 barrels. Much marble is used as an 
ornamental building stone. Until recently, it has been quarried on 
a large scale only in the East. Vermont supplies about four-fifths of 
all the marble used in the United States for ornamental work, but 
Colorado promises to become a great producer. 

Slates are used chiefly as roofing material, but also for various 
other purposes. The production of slate, like that of marble, is 
confined largely to the East, and is most important in Pennsylvania, 
Vermont, and New York. Sandstone is used for buildings, bridges, 
and other purposes. It is distributed widely in many states, so 
that many small quarries serve local needs. A few popular kinds 
of sandstone, such as the brownstone from Pennsylvania and the 
vicinity of New York City, have wider markets. 

Gypsum is used extensively for building-plaster and certain 
cements. It is used also as a land fertilizer, and in other ways. 

Clays and clay products. Clays have a wider distribution 
than most other economic rock materials, and are used in making 
many things. Among these are pottery of various grades, tiles, 
terra cotta, brick, and Portland cement (made from a mixture of 
clay and lime rock). Every state produces clay products, Ohio, 
Pennsylvania, New Jersey, and Illinois leading in the order named. 
The total value of the products of the clay-working industries of the 
country exceeded $162,000,000 in 191 1. 

Substitution of mineral products for wood. Brick, stone, 
and cement are being substituted more and more for wood in build- 
ings, sidewalks, bridges, piers, etc. This is highly desirable, because 
these materials are (1) more durable, (2) less liable to fire, and (3) 
their use lessens the drain on the forests. 

Mineral Fuels 
Coal. After soil, coal is the most important of the mineral 
resources. Together with iron, which is next in importance, it has 
made possible the extraordinary industrial development of the 
United States. Germany and England also have become great manu- 
facturing nations largely because of their extensive deposits of coal 
and iron. The United States has more and better coal than any other 
country, so far as known. Fig. 85 shows the general distribution 
of its coal fields. Their combined area is about 500,000 square miles, 



COAL SUPPLY OF THE UNITED STATES 



177 



or about 16 per cent of the area of the country. Their wide distribu- 
tion is a matter of great importance, since the largest item in the cost 
of coal is the cost of transportation. The amount of coal in the 
United States at the beginning of 191 1 was estimated at more than 
3,062,800,000,000 tons. About one-third of this, however, is accessi- 
ble only with difficulty, and by no means all of it is of good quality. 





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r^T^^ 




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nil 


















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L_^j% 


/ « 


1 ' 






ka ^h 




^7 


••3? 






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/■ XWCWV COAL 
FIELDS 
WM DOUBTFUL 

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\ K 1 coat (/A/of» 

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Fig. 85. Map showing general distribution of coal fields in the United States. 
(U. S. Geol. Surv.) 



It is estimated that more than 99 per cent of the original supply of 
coal in the United States is still in the ground. 

The mining of coal in the United States began to be important 
about the middle of the last century, and the output has nearly 
doubled each decade since. The 496,000,000 tons mined in 191 1 
was about V17 of all mined to the end of that year. If the output 
should continue to increase at the same rate, the entire known supply 
would be exhausted in less than 150 years. For various reasons, 
howxver, our supply of coal will last much longer than this. Never- 
theless, it is highly desirable (1) to avoid, so far as possible, the 
waste of coal; (2) to substitute water power for steam power (gen- 
erated by the burning of coal) wherever practicable; and (3) to use 
coal in the most efficient way possible. The waste in mining coal 
has amounted to about 50 per cent of the quantity produced; that 



i 7 8 



MATERIALS OF THE LAND— THEIR USES 



is, about 250,000,000 tons were wasted in this way in 191 1. This 
is more coal than was mined in the United Kingdom (the second 
coal-producing country) in 1905. Much unburned coal passes off 
as smoke. The average steam engine does not develop into power 
more than 6 to 10 per cent of the heat energy of the coal. In 
making electric light from coal, only a small part of one per cent 
of the energy of the coal is utilized. Much of this waste can be 




Fig. 86. Map showing general distribution of petroleum and natural gas 
fields (the black areas) of United States. (Day, U. S. Geol. Surv.) 

avoided, and some progress in this direction has been made already. 
One effect of the burning of large quantities of coal is to increase 
the amount of carbon dioxide in the air (p. 30). Indeed, it has 
been estimated that the amount may be doubled in this way in the 
next 1,500 years. It will be remembered (p. 31) that this probably 
would make the climate much milder. 

Pennsylvania, West Virginia, Illinois, and Ohio lead in mining 
coal. They have produced about ^4 of all the coal mined in the 
United States. 

Petroleum. Petroleum was discovered in large quantities in west- 
ern Pennsylvania in 1859. The field which includes this original area 
extends from New York to Tennessee (Fig. 86), and has produced 
more petroleum than any other. The output is now decreasing, 



SUPPLY OF IRON IN THE UNITED STATES 179 

however. Most of the petroleum of this field is of high grade. The 
large Ohio-Indiana field was the second to come into use (about 1885). 
Most of the others are of recent development. In 191 1, California 
produced most petroleum, and Oklahoma and Illinois ranked second 
and third. The total output of the country during this year was 
more than 220,000,000 barrels. Since i860, as much petroleum has 
been produced each nine years as in all preceding years, and should 
this rate continue, the supply, so far as it can be estimated in known 
fields, would be exhausted by about 1935. Should the present output 
continue without increase, the calculated supply will last until about 
the year 2000. 

Crude oil is used for fuel, for the prevention of dust on roads, and 
for some other purposes. From it various oils are manufactured 
for lighting and lubricating purposes, and many by-products are 
obtained. In view of the probable early exhaustion of the supply, 
petroleum should be used only for those purposes for which it is 
best adapted. Its most essential use is for the making of oils for 
lubricating the bearings of all kinds of machinery. For this purpose, 
no satisfactory substitute is known. On the other hand, the use of 
petroleum as fuel in locomotives and for the development of power 
in factories is in most places unnecessary, and should be discouraged. 

Natural gas. Natural gas is the most perfect fuel. So far as 
known, the United States has a greater supply than any other nation, 
and it occurs in more than half the states (Fig. 86). It is believed, 
however, that the natural gas now known will be exhausted within 
the next twenty-five or thirty years. In spite of this, and in spite of 
its great value, enormous quantities (estimated at 1,000,000,000 
cubic feet daily) are allowed to escape from the ground unused. A 
large part of this waste can be prevented. 

Metals 

Iron. Some iron was mined in this country in the colonial 
period. The production was unimportant, however, till 1850. Since 
then it has increased rapidly, so that the output during the decade 
ending with 1909 amounted to 52.6 per cent of all the iron ore that has 
been mined in the United States. 

It was estimated recently that the available iron ore (that usable 
under existing conditions) in the United States amounts to nearly 
4,800,000,000 long tons (a long ton is 2,240 lbs.), and that in addition 
there are low grade ores, part or all of which will be useful in the future, 



180 MATERIALS OF THE LAND— THEIR USES 

amounting to more than 75,000,000,000 long tons. Like coal, iron 
ore is distributed widely (Fig. 87), but by far the most important 
deposits of our country are in the Lake Superior region, especially 
in northern Michigan and Minnesota. This district contains about 
73 per cent of the available ore of the United States, and about 95 
per cent, of the low-grade reserve. It had produced, to the end of 
191 1, more than 530,000,000 long tons of iron ore — considerably more 



^r^^--^ 






1 




.i I 




^Yy^. 


p-5^3^ 




j 




I* *• / * i* #7' - 

1 \ '/ * 


• • 1 










m 


\ji 


-v 


^"^K ) 


1 










n * \ 







Fig. 87. Map showing general distribution of iron ore in the United States 
Some of the smaller areas contain more and richer ore than the larger ones. 



than half the total amount produced in the United States. In recent 
years it has furnished about 80 per cent of the entire output of the 
country. In 1910, the United States produced more than 56,800,000 
long tons of iron ore — nearly half the world's production for the year. 
In 191 1, however, the output was only about 41,000,000 tons. 

If the iron ores of the United States continue to be mined at the 
increasing rate of the last few decades, the known deposits of high 
grade will all be mined in about ninety years. Several considerations, 
however, make it certain that the supply of ore will last much longer. 
Furthermore, iron, unlike coal, can be used again and again. For 
example, old rails are made over into new ones or into other things. 
The great problem in conserving the supply of iron is therefore to 
use it again and again, keeping the stock as nearly intact as possible. 
There is little waste of iron ore in mining. 



COPPER, GOLD, AND SILVER 181 

Copper. The existence of copper on the southern shore of 
Lake Superior (Keweenaw Point) was known to the Indians at an 
early date. As late as 1845, however, the entire output in the United 
States amounted to only 100 tons a year, and not till 1867 did copper 
begin to be used in large amounts. Its use has increased rapidly in 
recent years, about 550,000 tons being produced in 1911. Nearly 
three-fifths of the entire amount produced in the United States have 
been mined in the last ten years. Michigan, long the leading copper 
state, is now outranked by Arizona and Montana. Some nine other 
states, most of them in the West, produce copper, several of them 
in large amounts. 

Copper ores are scattered so widely, and are so irregular in their 
occurrence, that the supply has not been estimated accurately. 
It is thought, however, that the known copper ore, usable at existing 
prices, will be exhausted in Michigan in fifteen or twenty years, and 
in Montana and Arizona in even less time.- Should the value of copper 
increase, lower grade ore could be used. Even now, at the Michigan 
mines, only twenty-two pounds of copper are obtained, on the average, 
from each ton of ore. New discoveries of copper are made from time 
to time, and for this and other reasons, copper ore will last much 
longer than the time suggested above. 

Copper is used chiefly for making wire and brass. These uses 
involve little unavoidable waste, and the same copper may be used 
repeatedly. 

Gold. The production of gold was unimportant in the United 
States until after its discovery in California in 1848. The leading 
gold-producing states are California, Colorado, and Nevada. Each 
produces about 1,000,000 ounces (an ounce is worth about $20) of 
gold per year. Alaska is also a heavy producer. The amount of gold 
which remains to be mined cannot be estimated. It already is practi- 
cable to mine very low grade ore. In some cases, for example, a ton 
of ore is mined and milled to recover one-eighth of an ounce of gold. 
Gold is used chiefly as coin and bullion, and in the arts. Most of its 
uses involve little waste or loss of the gold itself. Even were the 
supply used up, the loss would be much less serious than that of coal 
or iron. 

Silver. Neither the amount nor the duration of the silver 
deposits of the United States can be estimated. Nevada, Montana, 
and Utah are (19 10) the leading silver-producing states, followed 
by Colorado and Idaho. Like gold, silver is used chiefly for coin and 



182 MATERIALS OF THE LAND — THEIR USES 

in the arts. Its use in photography is an interesting and a rapidly 
increasing one. In general, there is little waste or loss in its use. 

Lead and zinc. Lead was known to the Indians of the Missis- 
sippi Valley before the coming of the whites, but the deposits of 
the region were not worked effectively until the early 1820's, when 
a period of great activity in mining began. This culminated in 
Illinois and Wisconsin about 1845. During the next few years 
many of the miners went to the iron fields of Lake Superior, and 
to the gold fields of California. Lead was discovered later in 
various western states, in many places in association with silver. 
Missouri is the leading lead-producing state, followed by Idaho and 
Utah. 

The known supply of lead is very limited. Much is lost need- 
lessly by the prevailing methods of mining, milling, and smelting. 
About one-third of the lead produced in the United States is used in 
making paint. Lead used in paint can be used but once, and more 
abundant things will have to be substituted for it increasingly in the 
future. 

Zinc is associated in many places with lead, and for years was 
regarded as valueless by lead miners. The first zinc plants were 
erected in Illinois in the 1850's, but for twenty years the produc- 
tion was small. In recent years it has increased very fast, and 
the output of the last decade equaled that of all earlier years. Mis- 
souri leads, by a large margin, in its production. There is great waste 
of zinc in mining, concentrating, and smelting. About two-thirds 
of that produced in this country is used for galvanizing iron. Like 
lead, it is used also for making paint. Most of the rest is used (with 
copper) for making brass, and for sheet zinc. 

In 191 1, the United States produced 406,000 tons of lead and 
271,000 tons of zinc. 

Aluminum. Aluminum is by far the most abundant of the 
metals. It is a constituent of many rocks, and makes up more than 
8 per cent of the earth's crust. It is light, strong, malleable, ductile, 
is a good conductor of electricity, takes and retains a high polish, 
and does not corrode easily. These properties fit it for many purposes, 
but the difficulty and expense of separating it from its combinations 
long prevented its extensive use. It is extracted on a commercial 
scale only from bauxite, a relatively scarce mineral. When it can be 
obtained cheaply from clay, of which it forms a part, its use wiU be 
increased enormously. 



CONSERVATION OF MINERAL RESOURCES 183 

The production of aluminum in the United States increased from 
&$ pounds in 1883 to about 47,000,000 pounds in 191 1. It 
is used for making a constantly increasing variety of things, such 
as cooking utensils, castings, wall " paper," ceiling panels, paints, 
varnishes, and wire. Doubtless in the future it will replace iron, 
copper, and some of the other metals for many purposes. 

Salt 
Salt is indispensable to man, and fortunately the supply is prac- 
tically inexhaustible. (1) In arid regions there are many lakes 
with no outlets into which streams bring minerals (including com- 
mon salt) that have been dissolved during the passage of the water 
through or over the rocks (p. 211). These things are left behind as 
water evaporates from the lake, which becomes more and more 
saline as the process continues. When the waters of the lake become 
saturated, further evaporation causes the minerals to begin to be 
precipitated from solution. Great Salt Lake is estimated to contain 
some 400,000,000 tons of common salt. (2) Extensive salt beds 
which were laid down in ancient lakes or arms of the sea are found 
between beds of other rock in many places. Those in central New 
York may have an area underground of some 10,000 square miles (lar- 
ger than Vermont), and single beds are in places 80 feet thick. Besides 
New York, Michigan and Kansas are leading salt-producing states. 
(3) The ocean is the remaining and greatest source of supply (p. 144). 

The need of salt helped to hold most of the American colonists near the At- 
lantic coast for along time. Not until it was discovered in the Holston and Kanaw- 
ha valleys (Tenn. and W. Va.), in central New York, and in Kentucky, did 
dependence on the coast for salt cease. In 1778, salt brought on pack animals 
over the Appalachian Mountains sold in southwestern Pennsylvania for £6 10s. 
per bushel. The same amount of salt now is worth but little more than 10 cents 
where it is prepared, and not more than 50 cents in the markets in most parts of 
the United States. 

Conservation of Mineral Resources 

The mineral resources noted above are a part of the heritage 
of the earth. The people of to-day have a right to use such of them 
as they need, in as great quantities as necessary. It is their duty, 
however, to use them in such a way as to insure the minimum of 
waste and the maximum of efficiency. This is demanded alike 
by the interests of the present generation, and by those of genera- 



i8 4 MATERIALS OF THE LAND — THEIR USES 

tions to come. The facts given show that many reforms are needed. 
The reckless waste of some of these resources is a reflection upon 
American intelligence. 

Questions 

i. What are the principal ways in which soil is being formed in New England? 
Florida? Nevada? 

2. Why are the soils of the lower flood-plains and deltas of large rivers of great 
fertility in most cases? Are they commonly of coarse or fine texture? Why? 

3. State conditions which explain why soil wash is, in some cases, much faster 
on one of two equal slopes than on the other. 

4. Would you expect wash in winter from bare fields to be greater in northern 
or southern United States? Why? 

5. Would it be desirable, from the standpoint of agriculture, entirely to 
prevent soil erosion if it were possible? Reasons? 

6. Tile underdraining is in many cases effective in checking soil erosion. Why? 

7. Plowing under straw, leaves, etc., was formerly a common practice. What 
value, if any, would this have? 

8. In some of the mountainous areas of Italy, Austria, and other countries, 
forests are maintained in strips at right angles to the slope of the surface, while 
the land between is tilled. Why is this advantageous? 

9. Explain in detail why plowing up and down a hill-side is unwise. 

10. Other things being equal, would you expect crops to suffer more from 
protracted droughts on sandy or on clayey soils? Why? 

11. In parts of China it is customary to plant alternate rows of leguminous 
plants (like peas and beans) and grains. How does this benefit the soil? 

12. Steel cars rapidly are replacing wooden ones, and re-enforced concrete 
(i.e., cement strengthened by steel) is being used for many new bridges in place of 
steel. Are these changes desirable from the standpoint of the conservation of 
natural resources? Reasons? 

13. Why are gold and silver, the "precious metals," much less essential to 
man than coal and iron? 



CHAPTER XIV 

CHANGES OF THE EARTH'S SURFACE DUE TO INTERNAL 

FORCES 

Slow Crustal Movements 

Except for occasional earthquakes and landslides the crust of the 
earth seems to be firm and stable, but it is in reality subject to very 
slow movements which, in the course of ages, produce great changes. 
Such movements warp both land and sea-bottom. It is probable 
that more of the earth's surface has been sinking or rising in recent 
geological times than has been standing still. 

Movement of coastal lands, (i) Old buildings and docks, 
near sea-level when built, are now under water in some places and 
well above the sea in others. Clearly, this means a recent change, at 
these places, in the relations of land and sea. (2) Beds of sediment 
containing sea-shells, deposited beneath the sea in recent times, are 
found above the water in north Greenland, on the Pacific coast of the 
United States, in the West Indies, on the west coast of South America, 
and in other places. On the slopes of Mount St. Elias, Alaska, mod- 
ern sea-shells have been found attached to the rocks just as they 
once grew, but several thousand feet above the sea. (3) On the 
other hand, there are drowned forests along some coasts. Thus north 
of Liverpool, England, many stumps may be seen at low tide standing 
on the beach (Fig. 88). Since trees of the kind represented by these 
stumps do not grow in salt-water, it is clear that the land where they 
grew has sunk below the level of high water. On the coasts of New 
Jersey and North Carolina, too, there are stumps having similar 
histories, several feet below sea-level. These and many other facts 
prove that the land and sea change their relations to each other, and 
that most coast-lines have been affected by such changes in recent 
times. 

The emergence of land may be due to (1) its rise, or (2) the sink- 
ing of the sea-level. Similarly, the submergence of land may be 
due to (1) its sinking, or (2) the rise of the sea. From what is now 

185 



i86 



CHANGES OF THE EARTH'S SURFACE 



known it is certain that both the sea and the land rise and fall from 
time to time. 

Causes of changes in sea-level. Several things may make the 
sea-level rise or fall, (i) The sinking of a part of the ocean bed would 
lower the sea surface, while the elevation of a part of the sea floor 
would have an opposite effect. (2) Sediment washed from the land 

into the sea builds up the 
ocean floor, and so raises 
the surface of the sea. 
(3) Lavas poured out 
from volcanoes beneath 
the sea, and the deposits 
of corals and shell-bear- 
ing sea life, make the 
sea-level rise. (4) An 
increase or decrease in 
the total amount of land- 
water or ice would lower 
or raise the surface of 
the ocean. Since the 
oceans are all connected 
one with another, each 
of the above changes 
would affect the surface 
of the sea everywhere, and by the same amount. Other factors 
also affect the surface of the sea, and some of them make it higher 
in certain places than in others. 

Changes of level in the interiors of continents. Changes of 
level are perhaps as common in the interiors of continents as along 
coasts, but they are not detected so easily, since there is no level 
surface like the sea with which to make comparisons. There are 
raised beaches about many lakes, as about the Great Lakes and 
Great Salt Lake (Fig. 89) ; but raised beaches about a lake may result 
from the lowering of the lake, either by the cutting down of its outlet 
or by evaporation. They do not, therefore, prove a rise of the land. 
But many old shore-lines about lakes are not horizontal, as they were 
when formed. Some parts of the old shore-line about former Lake 
Bonneville (the ancestor of Great Salt Lake) are 300 feet higher than 
other parts of the same line. Similar tilted shore-lines are found about 
many lakes, and show that the land has warped since the shore-lines 




Fig. 88. Stumps laid bare on the beach 
at low tide; Leasovve, England. (From photo- 
graph by Ward.) 



CHANGES OF LEVEL 



187 



were formed. Other phenomena, some of them discussed later, also 
show movement of large interior areas. 

Ancient changes of level. Layers of rock, deposited long ago 
as sediment beneath the sea, are now found over great areas, far 
above sea-level. Most of the solid rock beneath the Mississippi 
Basin, for example, was laid down as sediment beneath the sea, as 
shown by the shells of the sea animals which it contains. In the 




Fig. 89. Shore of former Lake Bonneville, Utah. (From photograph by 
U. S. Geol. Surv.) 

Appalachian Mountains, rocks formed in the same way are found 
up to heights of several thousand feet; in the Rocky Mountains 
up to 10,000 feet and more; and in some other mountains to still 
greater heights. It is certain, therefore, that changes of level have 
been great, and that vast areas have been affected. 

It is also certain that great changes in the areas and in the rela- 
tions of land and sea have occurred many times in the distant past. 



Earthquakes 

Frequency and importance. Tremblings or quakings of the 
earth's surface occur frequently in many countries. Most of them 
are not felt, and can be detected only by means of delicate instru- 



i88 



CHANGES OF THE EARTH'S SURFACE 



ments made to record them. For many years an average of several 
earth tremors a day have been recorded in Japan, and it has been said 
that some part of the earth's surface is shaking all the time. The 
changes made in the surface of the land by earthquakes are slight, 
and they are important chiefly because severe earthquakes may cause 
great loss of life and property. 

Distribution. Most earthquake regions lie near the edges of 
the continental platforms, though some (in Asia) are far inland. Most 

of them are mountainous areas, 
though some are lowlands. 
Earthquakes are perhaps most 
common in volcanic regions, 
though not all the earthquakes 
of such regions have been 
caused by volcanoes. Except 
along the west coast of South 
America, the southern conti- 
nents are rather free from 
earthquakes, or at least few are 
reported from them. In the 
northern hemisphere, earth- 
quakes are most common about 
the Mediterranean Sea, in 
southern Asia, in the islands 
east and southeast of that con- 
tinent, and along the western 
coasts of North and Central 
America. Some of the areas most affected by earthquakes are 
settled densely. 

Causes of earthquakes. Earthquakes are caused in various ways. 
During movements of the earth's crust, great cracks or fissures 
sometimes are formed in the surface of the land (Fig. 90). The walls 
of fissures may be displaced, or faulted. Faulting has caused many 
great earthquakes, the slipping of one great body of rock past another 
producing vibrations, which in some cases have spread great distances. 
An Alaskan earthquake in 1899 was caused by a sudden displacement 
of more than 40 feet, and the San Francisco disaster in 1906 resulted 
from a horizontal movement of 5 to 20 or more feet, along a line many 
miles in length. Earthquakes accompany violent volcanic eruptions, 
and in these cases the explosions which accompany the eruptions 




Fig. 90. 



Fissure in floor of Kilauea, 
Hawaii. 



DESTRUCTION BY EARTHQUAKES 



189 



doubtless cause the quaking. Great landslides and avalanches 
may cause slight earthquakes. Slight shocks may be caused in still 
other ways. 

It is probable that most earthquakes are incidents of the wide- 
spread movements to which the crust of the earth is subject, move- 
ments which are due chiefly to the continued fitting of the outside of 
the earth to a shrinking interior. In general, these movements are 
too slow to produce vibrations which we can feel ; but they are sufficient, 
in rare cases, to produce great earthquakes. 

Destruction of life and property. Except along the plane of 
slipping, the actual movement of the land surface during an earth- 




Fig. 91. The new library building at Stanford University, after the earth- 
quake of April, 1906. (Moran.) 



quake is very slight, in most cases only a small fraction of an inch. 
It is the suddenness of the shock which overthrows and destroys 
buildings and other objects. That a sudden but very slight movement 
of the ground may do this is clear from the fact that a quick, sharp 
tap on the side of a table may overthrow all loose objects upon it, 
even though the movement of the table itself is very slight. 

Some earthquakes in thickly settled regions have caused an appal- 
ling loss of life and property. The most disastrous earthquake in 
North America occurred in and about San Francisco in April, 1906, 
A large part of the city was burned by the fire which followed the 
shock. More than 700 lives were lost, and between 100,000 and 
200,000 people were made homeless. Some 25,000 buildings (Fig. 91) 



190 



CHANGES OF THE EARTH'S SURFACE 



were destroyed in the earthquake and fire, having an estimated value 
of more than $100,000,000. In 1905 a great earthquake in India 




Fig. 92. Taal Volcano, Philippine Islands, in eruption. (Gilchrist.) 

destroyed nearly 1 9,000 lives and more than 112 ,000 buildings. About 
1 00,000 people were killed in the earthquakes in southern Italy in 1908. 






TYPES OF VOLCANOES 



191 



In some countries where earthquakes are frequent, like Japan, 
much attention has been given to making buildings in such a way as 
to withstand the shocks. The greater frequency of earthquakes 
in Nicaragua was one reason for selecting the Panama route for the 
Isthmian Canal. 

When an earthquake disturbs the sea-bottom, waves are set in 
motion. These waves rush upon neighboring coasts, and in some cases 
(e. g., in Sicily in 1908) they have done great damage. Millions of 
marine animals and plants were killed during the Alaskan earthquake 
of 1899. 

VULCANISM 

Volcanoes 

A volcano is a vent in the earth's crust out of which hot rock 
comes (Fig. 92). The hot rock may flow out in liquid form (called 
lava), or it may be thrown out violently in solid pieces. It is gen- 
erally built up into a 
cone (Fig. 93), which 
may become a mound, a 
high hill, or even a high 
mountain. Quantities 
of gases and vapors are 
discharged along with 
the hot rock. There is 
a hollow, called the 
crater, in the top of 
most volcanic cones. 
Craters vary greatly in 
size, some of the larger 
ones being two or three 
miles across. While 
the volcano is active, 
an opening leads down 
from the crater to the source of the lava, at an unknown depth. 

Common phenomena of an eruption. In the explosive type 
of eruption, rumblings and earthquake shocks, due to explosions 
within the throat of the volcano, may occur for weeks or months 
before a violent outbreak.. During a violent outbreak, dust, cinders, 
and larger pieces of rock are shot forth and fall on the sides of the cone. 
The clouds of condensed steam and dust rising from the crater darken 




Fig. 03. 
(Marshall.) 



Cone of Ngauruhoe, New Zealand. 



192 



CHANGES OF THE EARTH'S SURFACE 



the sky, and torrents of rain, falling on the fine dust, may form rivers 
of hot mud. Liquid lava may or may not accompany the discharge of 
solid material. In the quiet type of eruption, the lava rises in the 
crater and overflows its rim or, more often, breaks out through cracks 
in the side of the cone. There is little or no burning in a volcano, 
for there is little or nothing to burn. There is, therefore, no smoke. 
What appears as smoke is mostly cloud, blackened by volcanic dust. 
The products of volcanoes. Lava is a term applied both to 
the liquid rock which issues from a volcano, and to the solid rock 



,,-,.-> 




Fig. 94. Recent flow of lava from Kilauea, Hawaii. (U. S. Forest Service.) 



which results from its cooling (Fig. 94). Most of the solid materials 
blown out of a volcano are pieces of lava which became solid before 
they were shot out, or during their flight in the air. They include 
masses of rock tons in weight, and smaller pieces of all sizes down to 
particles of dust (commonly called volcanic ash). The dust in many 
cases is shot high into the air, and, being light, is scattered broadcast 
by the winds, some of it coming to rest thousands of miles away. 
The liquid lava and the larger solid pieces, on the other hand, stay 
near the vent. 

The gases and vapors which issue from volcanoes are of many 
kinds. Some are poisonous, and some are so hot as to be destructive 
to life, as in the case of Mont Pelee, in 1902 (p. 197). 



TOPOGRAPHIC EFFECTS OF VOLCANOES 



193 



Soils made by the decay of volcanic materials may be very 
fertile if well watered. The volcanic soils of the Spice Islands 
(Moluccas), Java, and other islands of the East Indies, support a 
luxuriant vegetation. 

Number. The number of active volcanoes is not known, but 
is estimated at 300 to 400. Something like two-thirds of them are 
on islands, and the rest on the continents. 

Distribution. The distribution of active volcanoes is shown in 
Fig. 95. Many are in belts, within which some are in lines. The 




• ACTIVE VOLCANOES 



RECENTLY EXTINCT VOLCANOES 



Fig. 95. Map showing the distribution of volcanoes. (Russell.) 

most marked belt nearly encircles the Pacific Ocean. The volcanoes 
of the West Indies and of Java and Sumatra sometimes are considered 
as forming branches of the main belt. Outside this belt, there are 
a number of volcanoes in and about the Mediterranean Sea, and 
there are others which are not connected with any well-marked 
system. 

Most volcanoes are in the sea or near it. Many are in moun- 
tain regions, though they do not occur in all mountains. Many of 
the active volcanoes are near the line where the continental plateaus 
descend to the ocean basins. Many volcanoes are in lands which 
have been raised or lowered recently. 

Topographic effects of volcanoes. Some volcanic cones are 
mountains of great size, like Mt. Rainier (Tacoma) in Washington, 



194 



CHANGES OF THE EARTH'S SURFACE 



Mt. Hood in Oregon (Fig. 96), Mt. Shasta in California, and Orizaba 
in Mexico. All. those named are so high that glaciers are found 

on their slopes. Vol- 



canic cones are far 
more numerous than 
volcanoes, for the 
cones of many ex- 
tinct volcanoes still 
remain. 

Many small islands 
and some large ones 
are due chiefly or 
wholly to the build- 
ing of volcanic cones 
on the ocean-bottom. 
The Aleutian Islands 

and the Hawaiian Islands were formed in this way. Iceland, too, 

is largely volcanic. 

Destruction of volcanic cones. Volcanic mountains, like all 

other elevations on the land, are subject to change and destruction. 




Fig. 96. Mt. Hood, a snow-capped mountain. 




Fig. 07. Portion of ("rater Lake, Oregon. (Copyright by Riser Photo Co.) 



DESTRUCTION OF VOLCANIC CONES 



i9S 



They may be destroyed partially by violent explosions. Again, the 
top of a volcanic mountain may sink, leaving a great hollow, or 
caldera. Crater Lake, Oregon (Fig. 97), the deepest lake in North 
America, is in a caldera five or six miles in diameter, and 4,000 feet 
deep. The lake is sur- 
rounded by steep walls 
900 to 2,200 feet high. 
Since the sinking of 
the top, a small cone, 
now an island in the 
lake, has been built. 

Volcanic cones, are 
destroyed also by the 
slow processes of weath- 
ering and erosion 
(p. 306). Wind and 

rain attack them as soon as they are formed, but the results are not 
striking until the volcano is extinct and the cone stops growing. The 
many cones of extinct volcanoes in western United States are in 
various stages of destruction. Some in Arizona, California (Fig. 98), 




Fig. 98. Typical cinder cone, Clayton Valley, 
California. 




Fig. 99. Mt. Shasta, a typical volcanic cone furrowed by erosion, but retain- 
ing its general form. (U. S. Geol. Surv.) 



Idaho, and Oregon were formed so recently that they have been 
eroded but little. Fig. 99 shows a high mountain built by a 
former volcano. It still retains its conical form, but its steep upper 
slopes are cut by ravines and valleys, several of which contain 
glaciers. 



196 



CHANGES OF THE EARTH'S SURFACE 



Destructiveness. Like earthquakes, some volcanoes have de- 
stroyed great numbers of lives and much property. During an erup- 
tion of Vesuvius in 79 A. D., Pompeii, a city of about 20,000 people, 




Fig. 100. The ruins of Pompeii. (Doseff.) 

was buried by cinders and ashes (Fig. 100), and Herculaneum was 
overwhelmed by streams of hot mud. Some of the later eruptions 
of this volcano also have been very destructive. That of 1631 



Forsaken I 



Lang I. 





Fig. 101 Fig. 102. 

Fig. 101. Krakatoa Island and surroundings before the eruption of 1883. 

Fig. 102. Krakatoa Island and surroundings after the eruption of 1883. 
The numbers indicate the depth of the water in fathoms (a fathom = 6 feet) in 
both figures. 

destroyed some 18,000 lives. One of the most violent and destructive 
volcanic eruptions known was that of 1883 in Krakatoa, an island 
between Sumatra and Java. About two-thirds of the island was 



LOSSES DUE TO VOLCANOES 



197 



blown away, and the sea is now nearly 1,000 feet deep where the center 
of the mountain formerly was (Figs. 101 and 102). Sea waves spread 
to Cape Horn, and possibly to the English Channel. On the shores 
of neighboring islands the water rose 50 feet. More than 36,000 
persons perished, mostly by drowning, and 295 villages were destroyed, 
wholly or partially. 

The volcano of Pelee is on the island of Martinique, at the eastern 
edge of the Caribbean Sea. Its cone descends by steep slopes to the 
sea on all sides but the 
south, where there is a 
plain on which the city of 
St. Pierre formerly stood. 
After slumbering for more 
than fifty years, the vol- 
cano became active in the 
spring of 1902. On May 
8th a heavy black cloud, 
probably composed of 
steam, sulphurous vapors, 
and dust, which had an 
estimated temperature of 
1,400° to 1,500° 




Fig. 103. The ruins of St. Pierre, Mar- 
tinique. (Hovey.) 



F., swept 
down through a gash in 
the crater's rim, and out 
over the plain to the south- 
west. In two minutes it struck the city of St. Pierre, five miles 
distant, which was demolished at once (Fig. 103). Buildings were 
thrown down, statues hurled to the ground, and trees torn up. 
Explosions were heard in the city as the cloud reached it, and flames 
burst out, started either by the heat of the gases, or by the red-hot 
particles of rock which the gases carried. A few minutes later a 
deluge of rain, mud, and stones fell, continuing the destruction. Only 
two people out of 30,000 survived the disaster. 

Igneous Phenomena Not Strictly Volcanic 
Fissure eruptions. Lava sometimes rises to the surface through 
great cracks instead of through the rather small vents of vol- 
canoes. From such cracks floods of lava may spread over the 
land for hundreds of miles. Many such lava floods once occurred 
in Oregon, Washington, and Idaho, where the former hills and 



CHANGES OF THE EARTH'S SURFACE 



\s\- 




xjv? jg 


for 










\---^— 1 


) i 


; L...._ 

i 
1 



Fig. 104. Lava flows of the North- 



west. 



valleys were buried, and a vast plateau 200,000 square miles or 
more in extent was built up (Fig. 104). In this lava plateau, the 

Snake River has cut a great 
canyon 4,000 feet deep in some 
places, and 15 miles wide. The 
walls of the canyon show that 
in some cases successive beds 
of lava are separated by 
layers of soil in which the 
roots and trunks of trees are 
preserved. 

An older and larger lava 
plateau, more dissected by 
erosion, occurs in central and 
southern India. Still others, 
now made rough by erosion, 
are found in northern Ireland 
and western Scotland. Some of the islands off Scotland are rem- 
nants of an old lava plateau. 

Intrusions of lava. Most of the lava forced upward from great 
depths probably fails to reach the surface, and hardens underground. 

Such rocks may be exposed at 
the surface through the wear- 
ing away of the rocks which 
overlay them. Great masses of 
intruded lava may bulge up the 
overlying strata, making domes 
(Fig. 105), some of which reach 
the size of mountains. The 
Henry Mountains of Utah are 
examples. In places, lava has 
been forced in between beds of 
rock, and into cracks in them 
(Fig. 106). 

Intrusions of lava may give 
rise to topographic features of 
importance after erosion has 
affected the regions where they 
occur, for the hardened lava is 
in many cases harder than its 




Fig. 106. Diagram showing lava 
which has been forced in between beds of 
rock (forming silk), and into cracks 
(forming dikes). What changes have oc- 
curred since the dike-rock was intruded? 



CAUSES OF VULCANISM 



199 



surroundings. Many dikes form ridges. Intruded sheets of lava, if 
they have been tilted from a horizontal position, may also form ridges, 
and these ridges may be so high as to be called mountains. The 
Palisade Ridge of the Hudson (Fig. 107), and most of the mountains 




Fig. 107. The face of the Palisade Ridge, west of the lower Hudson River. 



of the Connecticut Valley, are examples. The steep ridges so impor- 
tant in the battle of Gettysburg are smaller examples of the same 
sort. 

Causes of Vulcanism 

The causes of vulcanism are not well known. How the liquid 
rock is formed, the depth of its source, and how it makes its way to- 
ward the surface, are unsolved questions. The old notion that 
volcanic vents are connected with a liquid interior has been 
abandoned. 

It seems probable (1) that lava is being formed all the time, 
in spots, in the deep interior, and (2) that it is all the time finding 
its way toward the surface, but faster and in greater amounts at 
some times than at others. The places where the crust is weakest, 
that is, where there is movement, are the places most likely to afford 
the lava a place of escape. 



200 



CHANGES OF THE EARTH'S SURFACE 



Questions 

i. At the west end of the island of Crete, in the Mediterranean Sea, old docks, 
near sea-level when built, are found many feet above the water. At the east end 
of the island, ancient buildings are under water. Was the change in the relation 

of land and sea thus recorded due to 
movement of the sea surface, or of the 
land? Why could it not have been due to 
the other? 

2. How would the coast-line of North 
America be changed if the bottom of the 
Indian Ocean were to sink enough to lower 
the surface of that sea 200 feet? 

3. Other things being equal, which 
are more enduring, volcanic cones built of 
lava or of cinders? Why? 

4. Will soil form quickly or slowly 
on the recent (1902) volcanic deposits of Martinique and St. Vincent? Why? 

5. (1) What was the origin of the mountain in the right hand foreground of 
Fig. 108? The evidence? (2) Has much or little time elapsed since its formation? 
How told? (3) What is the probable history of the curving ridge at the left? 




Fig. 108. 



CHAPTER XV 
MODIFICATION OF LAND SURFACES BY EXTERNAL AGENTS 

The surface of the land is being changed all the time by various 
agents, especially by wind, by water in the ground, by running water, 
by ice, and in minor ways by different forms of life. 

The Work of the Wind 

Winds change land surfaces by taking dust and sand from certain 
places and depositing them in others. Wind-driven dust and sand 
may wear exposed surfaces of rock. 

Transportation. Desert winds often sweep up "clouds" of 
dust which may be seen for miles, and a single storm may move 
millions of tons of dust and sand. The dreaded simoon of the Sahara 
has been known to destroy entire caravans, death resulting from 
suffocation in the dust-laden air. While transportation by the wind 
is most important in arid regions, it is not confined to them. Dry 
sand and dust are blown about wherever they are exposed to the 
wind. 

Particles of dust are much heavier than air, and gravity tends 
to bring them down. Yet they may remain in the air for a long 
time (i) because they are so small that they do not fall readily, 
and (2) because there are many upward currents in the air which 
carry them up in spite of gravity. As a matter of fact, the dust of the 
air always is settling, and the supply is being renewed all the time. 
Dust in the air may be carried great distances. A severe storm in 
March, 1901, carried dust northward from the Sahara as far as 
Denmark. In 1883, volcanic dust from Krakatoa (p. 196) was 
carried around the earth by the upper winds in about two weeks, 
its progress being shown by the brilliant sunsets to which it 
gave rise. 

Abrasion. Sand blown against a rock has the effect of a sand- 
blast, and wears the rock away. Abundant wind-blown sand, driven 

201 



202 



MODIFICATION OF LAND SURFACES 




Fig. ioq. Rocks carved by the wind. 
(Bastin.) What inferences may be made 
concerning the character of the rocks? 



against projecting rocks, may carve them into fantastic forms (Fig. 
109). This process is of much importance in dry regions where the 

land is rough. In deserts and 
along sea coasts, telegraph poles 
have been cut off near the 
ground by wind-blown sand. 
In some such places, stones are 
piled about the bases of the 
poles to protect them (Fig. no). 
Wind deposits. Wind de- 
posits of sand and loess have 
been described (p. 165). Sand 
usually is blown along within a 
few feet of the ground, and is 
therefore likely to lodge about 
any obstacle which blocks its 
way. Mounds, hills, and ridges 
of wind-deposited sand are 
dunes, which range in height 
from a few feet to more than 400 feet. Small dunes are much more 
common than large ones. Dunes are found mostly near the sources 
of abundant dry sand. They are common 
■j|? along much of the Atlantic coast of the 

; j United States, where sand is washed up on 

the beach by waves. After drying, it is 
JMBfcjSta-^^^" blown about by the wind. Winds from the 
■Bk&X Jk ^ V wes ^ kl° w this sand into the sea, but those 

BfrSj6^JK^lf^^^ from other directions, especially from the 
-^K "' east, drift it up on the land. Dunes abound 

over thousands of square miles in the drier 
parts of the Great Plains, as in western 
Nebraska and western Kansas. They are 
largest and most numerous in still drier re- 
gions, as the Sahara. In some places, dunes 
are the most striking feature of the landscape. 
Sand is blown from the windward side 
of a dune and dropped on the leeward side, 
much of the time. This continued shifting 
of sand to the leeward side results in a slow migration of the dune. 
Farm lands have been covered in this way, and forests have been 



Fig. no. Telegraph 
pole in southern Califor- 
nia, deeply cut by wind- 
driven sand. (Menden- 
hall, U. S. Geol. Surv.) 



DAMAGE DONE BY SHIFTING SAND 203 




Fig. in. Dunes advancing on a forest. Little Point Sable, Michigan. 




Fig. 112. The last house in Riggs, Oregon, a village overwhelmed by sand 
dunes. (Gilbert, U. S. Geol. Surv.) 



204 



MODIFICATION OF LAND SURFACES 



buried (Fig. in). In some places sand buries buildings (Fig. 112), and 
causes much trouble along railways. The migration of dunes along 
some coasts is so disastrous that steps are taken to stop it. If a dune 
is covered with vegetation, its position is not likely to change so long 
as the plants remain, for they hold the sand. Trees, shrubs, and 
grasses which will grow in sand sometimes are planted on dunes to 
prevent further drifting (Fig. 113). This has been done at various 
points on the western coast of Europe, and to some extent in our 




Fig. 113. Sand dune reclamation, 
from photograph by Forest Service.) 



Manistee County, Michigan. (Sketch 



own country, as at San Francisco, where the westerly winds drift sand 
in from the shore. The amount of wind-blown sand not heaped up in 
dunes is probably far greater than that in dunes. 

Summary. The more important phases of the work of the 
atmosphere may be summarized here. (1) Of most importance is 
its work as an agent of weathering (pp.- 1 61-164). Through its 
effect on changes in temperature it helps to break rocks, and by 
the chemical action of its oxygen, carbon dioxide, and water vapor, 
it causes rocks to decay. Weathering prepares materials for removal 
by various agents of transportation. (2) The wind transports and 
deposits large amounts of fine material. Although most extensive 
in arid regions, this work has affected all land surfaces. Since the 
wind deposits much dust and sand in the sea, the general effect is 
to lower the lands and build up the ocean-bottoms. (3) Rocks are 
worn by wind-driven sand. This is most important in deserts, where 
the atmosphere is, in many places, the chief agent in wearing down 
the land. (4) By controlling the conditions of evaporation and pre- 



WATER UNDERGROUND 205 

cipitation, the atmosphere makes possible the work of streams and 
of glaciers, and the existence of land life. 

QUESTIONS 

1. Why are there many dunes on the eastern side of Lake Michigan, and but 
few on the western? 

2. In most dune areas there are many hollows among the sand hills. In 
what ways are such hollows formed? 

3. Why are dunes formed along some river valleys and not along others? 

4. What changes in natural conditions may stop dune-building in a given 
region? 

Ground-Water 
general considerations 

The fate of rain-water. The average annual rainfall of the 
United States is about thirty inches. This means that a total of 
about 1,500 cubic miles of water (enough to cover New England to 
a depth of about 1,000 feet) fall as rain or snow in this country each 
year. It is thought that about half of this water evaporates, that 
about one-third of it runs off over the surface, and that the remain- 
ing one-sixth is taken up by plants or sinks into the ground. 

The ground- water surface. It is possible almost anywhere 
to dig wells deep enough so that they will contain water all the time. 
This means that the surrounding rocks are full of water below the 
level of the water in the wells. The surface below which the ground 
is full of water in any given region is the water surface or water table 
for that region. In swamps and marshes the water table is at or 
near the surface of the ground, while in arid regions it may be hundreds 
of feet below. In humid regions it is seldom more than 50 or 60 feet 
below the surface. The position of the water table also varies from 
time to time. It is higher after heavy rains, and lower during and 
after long droughts. 

Amount of water underground. The pores and openings in 
the rocks below the water surface are full of water. Some porous 
rocks contain one-third or more of their volume of water; very com- 
pact rocks contain but little. In general, rocks near the surface have 
more and larger pores and cracks than those at greater depths. Pores 
and cracks become very small at the depth of a few thousand feet, 
and probably none exist below a depth of five or six miles. If this 
is true, water does not descend to greater depths. There is water 



206 



MODIFICATION OF LAND SURFACES 



enough underground so that, if it were brought to the surface, it 
would form a layer probably 500 to 1,000 feet deep. 

Circulation of ground-water. Ground-water is moving all the 
time. This is shown, for example, by the constant flow of springs, 
and by the fact that after a well is pumped "dry," it soon fills again 
to the former level, because water seeps in from the surrounding rocks. 
Ground-water moves because the water table is not level every- 
where, and the water moves from places where its surface is higher 
to places where it is lower. The water table is kept uneven, partly 





HE—^-S^sKSi 


iWk. ^sfc. ^$&®. 


,-^-JjBafWgK ' ^ — - _ _ ■ - - 




'.■,'■:■.....:.■:■.'..;■.: £o»rff ■■■ 



Fig. 114. Diagram showing the relation of the level of ground-water (the 
broken line) to the surface of the ground and to a lake and river. 



because of unequal rainfall, and partly because of the uneven surface 
of the land. Other things being equal, the water table is higher beneath 
high land, and lower beneath low land (Fig. 114). The water surface 
below the high land tends to sink until it is as low as that beneath 
the low land; but in moist climates it rains so often that the water 
surface under the hills almost never sinks to the level of the water in 
the surrounding low lands, before it is raised again by rains. 

Water which sinks to great depths commonly follows an irregular 
course. At first its movement is chiefly downward, and is rather 
rapid because of the many large cracks and pores in the rocks near the 
surface. Farther down, its movement is largely sideways (Why?). 
It may flow slowly for many miles along a crooked course, through 
small openings, before it reaches a passageway leading to the surface. 
Through such an opening it may issue with great force as a spring or 
flowing well. Fig. 115 suggests the intricate circulation of the water 
which issues in a deep-seated spring. Some water flows underground 
to the sea or to lakes, and issues as springs beneath them. Much 



MOVEMENTS OF GROUND-WATER 



207 




ground-water, too, seeps out in such small amounts that it does not 
appear to flow, and does not make a spring. 

Much ground-water is taken up by roots, passes up through the 
plants, and comes out through their leaves (is transpired) into the air. 
The amount of water returned to the air daily by forests through their 
foliage varies under different conditions from 1,000 to 20,000 or more 
pounds per acre, during the growing season. About 5,000 pounds 
of water are transpired by the foliage of corn-plants in the production 
of a bushel of corn. Again, 
water is evaporating from the 
ground most of the time, even 
in regions where the soil appears 
to be very dry. 

The rate at which ground-water 
moves depends chiefly on (1) the 
porosity of the rock or soil, ana (2) 
the pressure of the water. The rate 
at which water seeps through soils 
from irrigating ditches in the West is 
in most cases from one to eight feet 
per day; but in very porous soils it 
is sometimes 50 feet per day. In 
widespread beds of sandstone which 

underlie southern Wisconsin and northern Illinois, the rate of movement of ground- 
water is about half a mile a year. At this rate, rain-water which enters these beds 
100 miles from Chicago would reach that city in about 200 years. 

Knowledge of the circulation of the upper part of the ground- 
water is important to every family using well-water for household 
purposes. Polluted well-water is very common on farms which 
might have pure and wholesome water. Great numbers of wells 
are so situated that ground-water moves toward them from cess- 
pools and stables. Largely as a result of this, typhoid fever is more 
common in many farming regions than in most cities. 

Uses and functions of ground-water. Ground-water is of vital 
importance in the economy of the earth and in human affairs. (1) 
It is important to plants. It dissolves the mineral elements of plant 
food and carries tnem to the roots. The amount of water available 
for plants is the most important factor conditioning their life in many 
regions. (2) Underground water supplies all springs and wells, the 
sources from which perhaps three-fourths of the people of the United 
States obtain their water for household use. 



Fig. 115. Diagram showing the in- 
tricate underground drainage which issues 
in a deep-seated spring. (Geikie.) 



208 



MODIFICATION OF LAND SURFACES 



The distribution of population in eastern United States was influenced greatly 
by running water and natural springs^ until modern methods of well-digging were 
developed. Absence of springs, and the use for two years of the brackish water of 
the James River, were one cause of the high death-rate in the Jamestown colony. 
A supply of wholesome water helped to determine the location of the Pilgrim 
colony at Plymouth, and of the Puritan settlement at Boston. Many of the 
stockaded villages of the early western frontier were so located as to command a 
supply of water in the event of an Indian siege. The settlement of certain inter- 
stream areas in southern Wisconsin 
and in Illinois was delayed for years, 
partly because of the difficulty and 
expense of digging wells. In the arid 
West, springs and watering places 
determine the location of many vil- 
lages and farms, and influence the 
course of trails and roads (Fig. 116). 
Their location is shown on many maps 
for the benefit of travelers. 

Because of the importance of 
ground-water to plant, animal, 
and human life, it is highly de- 
sirable that the water table be 
kept near the surface of the 
ground. It is estimated that in 
eastern United States it has 
been lowered from 10 to 40 feet 
over large areas by cutting off 
forests and by careless methods 
of tillage which have increased 
the proportion of the rain-water that runs off over the surface. It is 
estimated that at least three-fourths of the shallow wells and springs 
have failed in this part of the country. (3) Ground-waters bring 
about important changes in the character of the rocks through which 
they pass. These changes take place slowly, but they are going on 
all the time. 

OUTFLOWING WATERS 

Hillside and fissure springs. Fig. 117 illustrates two kinds 
of springs. In the one, water descends through a porous bed of 
rock, c, to a layer, a, which is compact. Much of the water flows 
along this layer until the latter comes to the surface (out-crops), and 
there the water issues as a hillside spring, s. The great majority of 
springs are of this class, and most of them are small. In the other 




Fig. 116. Map showing springs (by 
circles) and roads in the region of Flag- 
staff, Arizona. (From San Francisco 
Mountain Sheet, U. S. Geol. Surv.) 



FLOWING WELLS AND SPRINGS 



209 



case (Fig. 117), the water moves through the porous layer, b, under 
pressure, until it reaches a crack which leads up to the surface. If 
the crack is open, the water will follow it up to the surface, as at s', 
forming a fissure spring. In such a situation there will be a spring 
only when the opening is lower than the water surface in the layer 




Fig. 117. Diagram to illustrate two types of springs, as explained in text. 

of rock which carries the water. This sort of spring is similar to a 
flowing well in principle, though in the latter case the opening is made 
by man. 

Artesian wells. Formerly, artesian wells were regarded as the 
same as flowing wells. Now, the name "artesian" often is applied to 
deep, drilled wells, whether they flow or not. Fig. 118 illustrates 







Fig. 118. Diagram illustrating the conditions necessary for flowing wells 

the conditions necessary for flowing wells. They are: (1) A porous 
layer or bed of rock, A, under one which is not porous, and which 
prevents the water from escaping upward until it is penetrated by the 
well hole, W. The porous bed must come to the surface in a region 
which is higher than the site of the well; and (2) enough rainfall where 
the porous bed comes to the surface to keep that bed well filled with 



2IO 



MODIFICATION OF LAND SURFACES 



water. Under these conditions, the water will gush up (Fig. 119), 

if a hole is made down to it. 

Flowing wells may be but a few feet deep, or they may be thousands of feet 
deep. Thus there is one in St. Louis nearly 4,000 feet deep, and many in New 
Jersey less than 100 feet in depth. Many villages and small cities get their water 
from artesian wells; but great cities, such as New York and Chicago, could not get 
enough in this way. Brooklyn obtains a part of its supply in this way, its artesian 
wells furnishing about 22,000,000 gallons per day. In parts of the West, artesian 

waters are used extensively for irrigation, as well 
as for domestic and other purposes. 

In some regions more wells have been drilled 
than are needed, and when not in use (in many 
cases this is the greater part of the time) the 
water from the flowing wells has been allowed to 
run off freely. This has reduced so greatly the 
pressure and the amount of water available, 
that villages and cities, formerly abundantly 
supplied from artesian wells, have been com- 
pelled to seek other sources of supply. This is 
the case, for example, in some parts of the 
Dakotas. In some of the arid states where the 
water problem is critical, as in California, strict 
laws exist to prevent the waste of artesian and 
other underground waters. 




Fig. 1 19. An artesian well at 
Lynch, Nebraska. Flows more 
than 3,000 gallons per minute. 
(Darton, U. S. Geol. Surv.) 



Geysers. Geysers are hot springs 
which erupt from time to time (Fig. 
120). So far as known, they occur only 
in a few regions of recent volcanic activ- 
ity — Yellowstone National Park, New 
Zealand, and Iceland. From a few geysers water is thrown to a height 
of 200 feet or more, by steam produced at some point in the geyser 
tube below the top of the water. It is believed that hot volcanic 
rocks make the water boil, and the expansion of the steam formed 
causes the eruptions. (How will the cooling of the rocks affect the 
frequency of eruptions? What will be the final fate of existing 
geysers?) Although interesting, geysers are of little importance. 

Other hot springs. Some springs are warm, and others are hot. 
Where spring-water is hot, it is in some cases because it has been 
in contact with lava which came up from greater depths so recently 
that it has not yet become cold. In other cases the heat may be 
due to chemical changes taking place beneath the surface. There 
are more than 3,000 hot springs in the Yellowstone National Park, 
and many others in different parts of the country. 



MINERAL WATERS 



211 



Mineral and medicinal springs. All spring-water has some 
mineral matter in solution; but a spring is not commonly called a 
mineral spring unless it contains (i) much mineral matter, (2) mineral 
matter which is unusual in spring- water, 
or (3) mineral matter which is conspic- 
uous either because of its color, odor, 
or taste. Many mineral springs are 
thought — and some rightly — to have 
healing properties, and so are known as 
medicinal springs. Many of the famous 
watering-places and resorts for invalids 
are at hot mineral springs. The Hot 
Springs of Arkansas, Virginia, South 
Dakota, and Carlsbad (Bohemia) are 
examples. Many springs which are 
charged with gases are called mineral 
and medicinal, even though their waters 
are worthless for healing purposes. In 
191 1 mineral water was sold from about 
700 springs in the United States. The 
amount of water sold was more than 
67,000,000 gallons, valued at about 
$7,800,000. 

WORK OF GROUND- WATER 

Solution. All water which comes 
out of the ground has in solution some 
mineral matter dissolved from the rock 
through which the water has passed. 
Pure water does not dissolve mineral 
matter readily; but rain-water is not 
pure, for it dissolves gases from the air, 
and in sinking through the soil takes up 
the products of plant decay. With these 

impurities in solution, ground-water dissolves most sorts of mineral 
matter more readily than pure water would. The amount of mineral 
matter brought to the surface through springs is very great. 

Much ground-water finds its way to rivers after it seeps out. 
The larger part of the mineral matter in solution in rivers has come 
from ground- water which has flowed to them. All the rivers of the 




Fig. 120. The Wairoa Gey- 
ser, New Zealand. Shoots 1 ,500 
feet. (New Zealand Gov't 
Tourist Dept.) 



212 MODIFICATION OF LAND SURFACES 

earth are estimated to carry nearly five billion tons of mineral matter 
to the sea in solution each year. The transfer of so much mineral 
matter in solution from land to sea, lowers the land. 

Some of the mineral matter carried to the sea in this way remains 
in the sea-water. Thus, most of the salt which has been carried to 
the sea remains there, probably, to this day. On the other hand, 
much of the mineral matter taken to the sea is used by sea animals 
(and some plants) for making their shells and bones, and these are 
left on the sea-bottom when the organisms die. 

Caverns and cavern life. By the dissolving work of ground-water, rock is 
made porous. Small pores and cavities are more numerous than large ones, but 
some of the openings made in this way, such as Mammoth Cave in Kentucky and 
Wyandotte Cave in southern Indiana, are very large. Such caves occur chiefly 
in limestone, for this is the most soluble of the common rocks. 

A few animals live in caves and some of them show peculiar features. They 
are colored less brightly than their relatives above ground. This is probably 
because of the absence of sunlight, which seems to have much to do with producing 
color in animals. Some cave animals have good eyes, some have poor eyes, and 
some have none. From these and other facts, we infer that the eyes of animals 
in dark caves tend to disappear. The organs of touch are well developed in 
cavern animals. In the darkness the sense of touch is much more useful than 
sight. 

In Europe, certain caverns were the homes of primitive man, as shown by the 
human bones and the tools which are found in them. Here, too, are found the 
bones of large animals which were killed for food or fur, and taken to the caves. 
On some of the bones of such animals, and on pieces of slate or wood, there are 
drawings, some of which are of animals no longer living in the region where the caves 
are. From this we infer that the people who lived in the caves dwelt there a long 
time ago. 

Deposition. Ground-water sometimes leaves a part of its dis- 
solved mineral matter in the pores and cracks of the rocks through 
which it flows. When cracks in the rocks are filled or partly filled 
by mineral matter deposited from solution, the fillings become veins 
(Fig. 121). Many ores of gold, silver, lead, zinc, copper, and other 
metals, occur in veins. Originally, most of the metals were scattered 
widely through the rocks. They were dissolved, and then deposited 
by ground-waters in the cracks and openings where they are now 
found. Thus ground-water has made the great deposits of most ores, 
so important to mankind (pp. 179-182). Ground-waters also deposit 
mineral matter among particles of loose sediment, cementing them 
into firm rock. 

Mineral matter brought to the surface by ground-water may 



WORK OF GROUND-WATER 



213 



be deposited there, as the result of various causes. (1) When water 
evaporates, the mineral matter dissolved in it is left behind. This 
is one reason why kettles in which water is boiled become coated with 
mineral matter. (2) Certain gases dissolved in water help it to dis- 
solve mineral matter. If water contains much gas, which later es- 
capes, as when the water is heated, some of the mineral matter in 
solution may be deposited. (3) Warm spring- water may give up 
what it holds in solution when it cools. (4) Microscopic plants grow 
in the waters which 
issue from some hot 
springs, as in Yellow- 
stone Park, and by 
some process not well 
understood extract 
mineral matter from 
the water, and cause 
it to be deposited. 

Solution and deposi- 
tion may be going on at 
the same time, in the same 
place. Thus the original 
material of a buried shell 
may be dissolved and car- 
ried away at the same 
time that other material 
is left in its place, pre- 
serving the form of the 
shell. In the same way, 
wood may be replaced by 
mineral matter, giving rise 
to petrified wood, or wood 
"turned to stone." Such 

changes probably take place slowly, the mineral matter which was in solution in 
the water replacing the woody matter as it decays. 




Fig. 121. A quartz vein (the white band) fill- 
ing a crack in much older rock. Muchals Caves, 
Kincardineshire, Scotland. 



Mechanical work. Mechanical wear by ground-water is slight, 
since ground-water rarely flows in strong streams. Indirectly, 
ground- water helps to bring about changes of another sort. When the 
soil on a steep slope becomes full of water, its weight is increased great- 
ly, and the water in it makes it move more easily. Under these cir- 
cumstances, it sometimes slides down. Such movements are known 
as slumping or sliding. If the slide is large, it usually is called a 



214 



MODIFICATION OF LAND SURFACES 




landslide (Fig. 122). Slumping is very common on the slopes of 
hills composed of clay or other loose matter. Many landslides have 

been very destructive. 

In 1903 there was a slide 
on Turtle Mountain, Prov- 
ince of Alberta, Canada. 
A huge mass of earth nearly 
half a mile square, and 
probably 400 to 500 feet 
deep, suddenly slid down 
the steep face of the moun- 
tain, into the valley below. 
The length of the slide was 
about two and a half miles, 
and it is estimated that the 
time which it took was not 
more than 100 seconds. 
The heavy rainfall of the 
preceding year had filled 
the rock with water, and 
the earth tremors which 
occurred shortly before the 
slide are believed to have 
hastened the catastrophe. 

Water in the soil 
and subsoil works with 
gravity in the ex- 
tremely slow, down- 
slope movement of 
surface material. This 
sort of movement is 
creep (Fig. 123), which 
is usually too ^slow to 
be seen. 



Fig. 122. A landslide, 
graph by Hole.) 



(Sketch from photo- 




Fig. 123. A ravine near Crawfordsville, In- 
diana, showing trees leaning down-slope, in part 
because of creep. The surface material creeps 
faster than that below, tipping the tree.s toward the 
axis of the ravine. 



SUMMARY 

From the preceding 
paragraphs it is ap- 
parent that the exist- 
ence and work of ground-water are matters of great importance. 
(1) Without water in the soil most plants could not live, and the 
amount available largely controls both the density and the- character 
of the vegetation. (2) Chiefly through its influence on plant life, 



WORK OF RUNNING WATER 215 

ground-water helps to determine the distribution and occupations of 
people. (3) Ground-water is the source of all wells and springs. 
Ground-water, seeping out, maintains the flow of most streams. (4) 
Ground- water may modify the character of rocks in several ways: 
(a) by removing soluble constituents; (b) by depositing new mate- 
rial in rock cavities; (c) by replacing old material with new; and 
(d) by favoring new chemical combinations. These changes must 
have occurred on a vast scale, for ground-waters have been at work 
for untold millions of years. As a result, soils and useful ores have 
been accumulated. (5) The mechanical work of ground-water is 
relatively unimportant, but widespread. The creeping and slump- 
ing of surface material are in some cases due partly to ground-water. 

QUESTIONS 

1. In order to contain water constantly, must wells extend farther below 
the surface of the ground on hill tops or in valley bottoms? 

2. In order to increase the flow of water, dynamite is sometimes exploded in 
wells. Why does this in many cases produce the desired effect? Would it be more 
likely to succeed with wells in hard, brittle rocks, or soft, tough rocks? 

3. Make a diagram showing (1) the surface of the ground in a hilly region con- 
taining a lake, a swamp, and a river, and (2) the position of the water table beneath 
this surface (a) after continued rains, and (b) during a long drought. 

4. What effect does the irrigation of arid lands by water led in ditches from 
streams have on the position of the water table? How does this affect the question 
of the acreage which may be irrigated in years to come? 

5. Why are the inscriptions on many old tombstones indistinct? 

6. Describe the characteristics of a climate which should (1) hinder, and (2) 
favor solution by ground-water. 



The Work of Streams 

Running water is more effective than wind in changing the sur- 
face of the land over which it moves, largely because water is about 
80 times heavier than air. The work of running water is also much 
more important than that of ice, because water moves more readily 
and affects larger areas. It is true that glaciers have been much more 
extensive than now at different times in the past, but this was the 
case, so far as known, only for comparatively short periods. On the 
other hand, streams are numerous in most lands, and have been for 
untold ages. All in all, running water is more important than all 
other agents- in shaping the details of land surfaces. 

Streams modify land surfaces (1) by moving loose material to 



2io MODIFICATION OF LAND SURFACES 

lower levels, much of it to the sea, (2) by wearing their channels, 
and (3) by depositing their excess loads in various forms. These 
phases of river work, together with their topographic results and 
some of their human relations, are discussed below. The use of 
streams, as for commerce, manufacturing, and irrigation, is discussed 
in Chapter XVI. 

TRANSPORTATION 

Gathering sediment. As rain-water Hows down the slopes on 
which it falls, it carries particles of earth to the streams below. A 
stream gets much sediment in this way, if the immediate run-off 
flows over bare, steep slopes of loose material, and little, if it flows 
over slopes well covered with vegetation, such as grass land or forest. 
Besides the sediment brought to it by slope wash, a stream also 
gathers material from its bed and banks. 

A stream is not a single, straightforward current. When water 
runs swiftly through an open ditch or gutter, some of it may be seen to 
move from sides to center, and some from center to sides, while 
eddies are common. There are also many subordinate currents in 
the main current of a river, and they move in various directions. 
Many of them are caused by the unevenness of the bed of the stream 

(Fig. 124). Some of them 
a move upward and carry 
sediment up from the bot- 
tom of the stream. 
_ ^ Ground-water dissolves 
///^~a~\\-* ^r^Tr^:.' rock slowly, and springs 

„. __ .„ , m bring some of this dissolved 

Fiiz:. 1 24. Diagram to illustrate the effect 7r * . ( \ 

of irregularities, a and 6, in a stream's bed, on matter to streams (p. 211 J. 
the current striking them. Most dissolved substances 

are invisible, and remain in 
the water even after it has become quiet. The amount of matter 
carried to the sea in solution each year by all rivers (p. 211) has 
been estimated to be about one-third as much as the sediment 
carried by them. 

Carrying sediment. Coarse materials, such as pebbles, in most 
cases are rolled along the bottom, while tine materials, such as mud 
and silt, are likely to be carried in suspension. The behavior of the 
fine sediment in suspension needs explanation. 

Mud consists chiefly of tiny particles of rock, nearly three times 
as heavy as water; hence they tend to sink all the time. But as 



TRANSPORTATION BY STREAMS 217 

gravity brings them down, many are caught by upward currents 
(Fig. 124), and carried up in spite of gravity. It is largely by means 
of these minor upward currents in the main stream, that sediment is 
kept in suspension. Particles of sediment suspended in a stream are 
dropped and picked up repeatedly, and the long journey of any particle 
is made up of many short ones. 

Amount of load. The amount of sediment a stream carries 
depends on (1) its swiftness, (2) its volume, and (3) the amount and 
kind of sediment which it can get. Swift and large streams can 
carry a heavier load than slow and small ones. The effect of velocity 
on the carrying power of streams may be seen in most creeks and 
rivers which are wider in some places than in others. Where the 
channel is narrow, the current is swift, and here, in many cases, 
all fine material has been swept away, leaving only pebbles and 
larger stones in the channel. Where the channel is wider, and 
the current slower, the bottom of the same stream may be covered 
with sand or mud. By narrowing the channel of the Mississippi 
by making jetties near one of its mouths, in 1875, James B. Eads 
not only prevented further deposition of sediment there, but forced 
the river to clear out its own channel. This change permitted 
larger ocean vessels to reach New Orleans. 

The amount of material which certain streams carry to the sea has been 
estimated. For a given river, the estimate is made by calculating the average 
amount of water (in gallons or in cubic feet) discharged by it each year, and then 
determining the average amount of sediment in each gallon or each cubic foot. 
The Mississippi River carries to the Gulf of Mexico an average of more than a mil- 
lion tons of sediment a day. It would take nearly 900 daily trains of 50 cars, each 
car loaded with 25 tons, to carry an equal amount of sand and mud to the Gulf. 
This sediment represents a great loss to the country (p. 167), for most of it would 
make soil of great fertility, if it were on land. All the rivers of the earth are carry- 
ing perhaps 40 times as much as the Mississippi. 

CORRASION 

How streams wear rocks. As already stated (p. 216), streams 
wear (corrode) their channels. If the channel is muddy, the mov- 
ing water picks up sediment; if sandy or gravelly, sediment is rolled 
along the bottom. Many streams flow on solid rocks, and they 
gather load even from them. Rock exposed to water, as in the bed 
of a stream, decays. As it decays, it crumbles, and the crumbled 
parts are swept away by a swift current. Again, the sand and 
gravel rolled along by a stream wear its bed even if it is of hard 



2l8 



MODIFICATION OF LAND SURFACES 



rock. Subordinate currents sometimes drive the sediment in suspen- 
sion against the bottom or sides of the channel with similar results. 
The bits of sediment which a stream carries therefore become tools 
(Fig. 125), with which even hard rock is worn away. Clear water, 
flowing over firm, hard rock, wears the rock little. This is shown 




Fig. 125. The tools of a river. 
Joe River, Washington. (Tolman.) 



Stream-worn pebbles in the bed of the St 



by the fact that in many cases even large rivers flowing from lakes 
have " mossy" channels. (Why do such rivers have few tools?) 

Rate of erosion. The rate at which a stream wears down the 
surface over which it flows depends largely on (1) its volume, and 
this depends chiefly on the amount of precipitation, and on the 
size and topography of the area draining to it; (2) its velocity, which 
is determined chiefly by its slope, or gradient, and its volume; (3) 
the character of its bed, especially the resistance of its materials; and 
(4) the load which the running water carries. To work most effec- 
tively, the water must have tools enough to enable it to cut rapidly, 
but not so many that the energy expended in moving them retards 
its flow seriously. Since the factors named above vary greatly, 
the rate at which the land is being worn down is very unequal in 
different places. The average rate of wear for the United States 
is thought to be about 1 inch in 760 years; but the rate varies from 



RIVER VALLEYS IN HISTORY 



219 



an average of 1 inch of reduction in about 440 years in the Colorado 
Basin, to 1 inch in about 3,900 years in the basin of the Red River of 
the North (Fig. 126). 

FEATURES DEVELOPED BY STREAM EROSION 

River Valleys 

The depressions in which rivers flow are their valleys, and in 
the making of valleys streams have been the chief agents. 

River valleys centers of human activity. Most of the great 
valley lowlands of middle latitudes are settled densely, because 




Fig. 126. Rates of land reduction by stream erosion in the United States. 
The figures are the approximate number of years required for one inch of reduction. 
(Dole and Stabler, U. S. Geol. Surv.) 



of their fertile soils, favorable topography, and facilities for com- 
munication. Probably more than one-fourth of the people of east- 
ern United States live on alluvial lands. 

The valleys of the United States have been sought out for set- 
tlement from the beginning of its history. New York history began 
at the mouth of the Hudson, Pennsylvania history in the valley 
of the Delaware, and that of Virginia on the banks of the James. 
Later, various valleys became highways of expansion toward the 
interior. The overflow from the settlements of the coastal low- 
lands of Massachusetts passed over the rocky and infertile uplands 



220 



MODIFICATION OF LAND SURFACES 



to the west, to the inviting bottom lands and terraces of the Con- 
necticut Valley. As years passed, this great valley led settlers 
northward into New Hampshire and Vermont. The Ohio Valley 

was one of the first 
sections of the inte- 
rior to be settled, and 
for many years the 
Ohio River was a 
main highway of 
westward expansion. 
The upper Rio Grande 
Valley guided settlers 
northward from Mex- 
ico into the United 
States. The Platte 
Valley directed many 
fur traders and trap- 
pers across the Great 
Plains; it was fol- 
lowed by the Mor- 
mons on their way to 
Utah; along it ran the 
Oregon Trail and the 
first trans-continental railroad; and it was the greatest gateway into 
Nebraska when, in the fifties, the latter began to be settled. Many 
other examples of the part which valleys have played in expansion 

and settlement might be 
given. 

The larger rivers of 
eastern United States 
were long the great high- 
ways of trade and travel. 
Much of the Interior 
depended largely on the 
Mississippi and its tribu- 
taries as outlets to market, before the building of railroads (p. 274). 
In the future, the larger rivers of the United States probably will 
be used more than now for transportation (p. 287). 

Many valleys are grown-up gullies. Many valleys are en- 
larged gullies. A gully started during one shower (Fig. 127) is made 




Fig. 127. A gully made by a single shower. 




Fig. 128. . Diagram illustrating how one gully 
takes others as a result of growth. 



FORMATION AND GROWTH OF VALLEYS 



221 



deeper, wider, and longer by the next. As the result of repeated 
showers year after year and, in many places, repeated meltings 




4*fefaMti^3SEE5 



Fig. 1 29. Gullying in southwestern Iowa. (Iowa State Drainage, Waterways, 
and Conservation Commission.) 

of snows, the gully grows to be a ravine, and later a valley. Not 
all gullies, however, become valleys. Many gullies may start on 
one slope, but as they 
grow, some are so 
widened as to take in 
others (Fig. 128), and 
the number is reduced. 
Few gullies become 
ravines, fewer still be- 
come small valleys, 
and the number of 
valleys which attain 
great length is very 
small. 

Growth of gullies 
should be prevented. 
Much land in the 
United States has been 
ruined and much more 
injured, by gullies. 
There are many exam- 




Fig. 130. Brush dams built to check erosion in 
the southern Appalachians. 



pies of such land in the southern Appalachians, where, on bare 
surfaces, gullies form and grow rapidly because the slopes are steep, 



I 

222 MODIFICATION OF LAND SURFACES 

the rainfall heavy, and much of the surface material is eroded easily. 
Surfaces of this sort should, as a rule, be given over to the growth of 
forests. But serious gullying is by no means confined to mountain 
areas (Fig. 129), and the problem of checking the growth of gullies 
is country-wide. One of the best ways of stopping their growth is by 
filling them with brush (Fig. 130). 

How valleys get streams. Water commonly flows in gullies 
only when it rains or when snow melts, and for a short time after- 
ward. But many valleys made from gullies have permanent streams, 

so that they are being 
made larger all the 
time. 
k When a valley has 
been deepened so that 
its bottom is below the 



T? . i^- u • j ground-water surface, 

Fig. 131. Diagram showing ground- water sur- & 

face; a, the ground-water surface in wet weather, ground-water seeps or 
and b, in times of drought. When a valley has been flows into it, and forms 
cut below a, there will be a stream in wet weather, , j -p- 

but it will go dry in time of drought. Whentheval- a stream - ^n^g-^ 1 * 
ley bottom is below b, the stream will be permanent. a represents the water 

surface in wet weather, 
and b the water surface in dry weather. The valley whose cross- 
section is shown by 1 does not have a stream fed by ground-water; 
the valley 2 has a small stream in wet weather; while the valley 3 has 
a permanent stream, because its bottom is below the ground-water 
level of dry times. 

Streams which are fed by lakes, and streams which flow from 
snow- and ice-fields which last from year to year, do not depend 
on ground-water, though in most cases they receive it. 

The deepening of valleys. Swift streams remove material from 
their beds and so make their valleys deeper, but many slow streams 
deposit more sediment than they take away, and so make their valleys 
shallower. Many streams deepen their valleys in their upper courses 
where their waters are swift, while they make them shallower in 
their lower courses where the flow is sluggish. As a stream deepens 
its valley, the gradient becomes less, and the stream flows more and 
more slowly. In time, every swift stream will cut its channel down 
until its gradient is low and its current sluggish. A stream cuts the 
lower end of its channel down to about the level of the lake, sea, or 
river into which it flows, but the channel rises from its lower end to 



FORMATION AND GROWTH OF VALLEYS 



223 





its head. The lowest level to which a stream can reduce its basin is 
base-level. 

The widening of valleys. Valleys are widened in many ways, 
among them the following: (1) A stream may flow against one 
side of its channel with such force as to undercut the slope above. 
Slow streams are more likely to 
widen their valleys in this way 
than swift ones, because they are 
turned more easily against their 
banks by obstacles in the channels. 
(2) Rain-water flowing down the 
slopes of a valley carries earthy 
material with it. This widens the 
valley, by slowly wearing back 
its slopes. (3) The loose matter 
which lies on the slopes of a 
valley creeps slowly downward, 
especially when wet. It may 
also slump down steep slopes. In 
these and other ways, all 
leys are being widened all 
time. 

After streams have cut their 
valleys down to low gradients, 
they make flats in their bottoms, 
by side-cutting (Fig. 132). These 
flats are below the level of the 
surface in which the valleys lie, 
and may become very wide (Fig. 
133). Thus the Mississippi River 
at Memphis has a flat about 35 
miles wide. Most valley flats increase 
regularly down stream (Why?). 

The lengthening of valleys. The headward growth of a gully 
is due chiefly to erosion by the water which flows into its upper 
end. The head of a gully advances in the direction of greatest 
wear, and this is rarely in a straight line. Most valleys are therefore 
crooked from the outset. 

The headward growth of a valley normally continues until the 
wear of the water flowing into its upper end is equaled by the wear 





Fig. 132. Diagrams of a 
making a flat by side cutting. 



in width more or less 



224 



MODIFICATION OF LAND SURFACES 



of the water flowing from the same divide (water-parting) in the 
opposite direction. The divide is then permanent (Fig. 134). 

Valleys are not all grown-up gullies. Not all valleys were 
formed by the growth of gullies. A vast area in northern North 




Fig. 133. A wide valley flat. Milk River, near the Montana-Alberta bound- 
ary. (From photograph by U. S. Geol. Surv.) 

America, for example, once was covered by a sheet of snow and 
ice. Most of the rivers which had existed in this area ceased to 
flow while the ice lay on the land. Many of their valleys were 

rilled, at least in places, by the drift 
which the ice left when it melted, 
and so great areas were left without 
well-defined valleys. The melting 
ice, however, supplied much water, 
and this flowed along the lowest 
lines of descent which it could reach, 
and made valleys along those lines. 
Valleys made by such waters may 
have permanent streams at the start, since they do not depend on 
ground-water. 

Again, the melting of the ice left many lakes in the hollows of 
the land it had covered, and the rainfall of the region was great 
enough to make many of them overflow. When a lake overflows, 



Fig. 134. Diagram of a divide. 
The crest of the divide (at A) is per- 
manent if the conditions of erosion 
are the same on the two sides. Rain- 
fall may lower it, but cannot shift 
its position horizontally. 



STAGES OF EROSION 



225 



the out-going water follows the lowest line of descent, and cuts out 
a valley. In these ways, rivers soon were formed on the surface 
from which the ice melted. 

Valley and river systems. Most valleys are joined by many 
smaller valleys. The reason is simple. The erosion of the slopes 
of valleys by the water flowing from them to the valley-bottoms is 
greater along some lines than others (Why?), and tributary gullies 
are started, which, growing in the same way as the parent valleys, 
may come to have permanent streams. These tributary valleys of the 
first generation come to have branches, and the process may go on 
until a network of watercourses affects the surface. 

A valley and its tributaries constitute a valley system. A stream 
and its branches form a river system, and the area drained by a river 
system is a drainage basin. 

Stages in the history of valleys and streams. Valleys grow in 
size as they advance in years. When a valley is young, it is narrow 
and its slopes are steep. If the land is high, the valley may have a 
steep gradient, in which case it soon becomes deep. Its cross-section 
is then somewhat V-shaped (Fig. 
135, 1), and its tributaries are short. 
A mature valley is wider (Fig. 135, 2), 
its slopes in most cases are gentler, 
and its tributaries are longer and 
older. An old valley is wide, and 
has a broad flat and a low gradient 
(Fig. 135, 3). 

A stream also, as well as its val- 
ley, passes from youth to maturity, 
and from maturity to old age. In 

its youth, it is likely to be swift, unless it flows through low land. 
In maturity, it flows less swiftly and more steadily, and when it 
reaches old age, it winds slowly through its wide plain. Even an old 
stream, however, may take on the vigor of youth when in flood. 

The terms youth, maturity, and old age may be applied to river 
systems as well as to single rivers. Every river system, aided by 
weathering, has entered on the task of carrying to the sea all the land 
of its basin which is above base-level. So long as the river system has 
the larger part of its task before it, it is young. When the main valleys 
have become wide and deep, and the areas of upland have been well 
cut up by valleys, the river system is said to have reached maturity. 




Fig. 135. Diagram showing 
changes in the shape of a valley as 
it advances from youth to old age. 
1 = youth; 3 = old age. The 
material in which the valley is cut 
is all of the same character. 



226 



MODIFICATION OF LAND SURFACES 



When the task of reducing its drainage basin to base-level is nearing 
completion, the river system has reached jld age. 

The topography of a drainage basin is youthful when its river 
system is youthful, mature when its river system is mature, and 




Fig. 136. Diagram of an area in a youthful stage of erosion. The area 
some distance from the sea. The bottom of the diagram represents sea-level. 




Fig. 137. Diagram showing mature topography in a region situated some 
distance from the sea. The bottom of the diagram is sea-level. The area shown 
in Fig. 136 will in time resemble closely the present appearance of this area. 




Fig. 138. Diagram showing old topography in a region situated some distance 
from the sea. The bottom of the diagram is sea-level. Unless the land is elevated, 
the areas represented in the two preceding figures will finally closely resemble this 
area. 

old when its drainage is old. In an area of youthful topography, 
much of the surface has not yet been much changed by erosion 
(Fig. 136), and the surface may be ill-drained. In an area of mature 
topography, much of the surface has been reduced to slopes by erosion 



STAGES OF EROSION 227 

(Fig. 137), and is well-drained; while an area of old topography is one 
which has been brought down to general flatness by erosion (Fig. 138). 
When an area is worn as low as running water can bring it, it 
is a base-level plain. As streams wear the land toward base-level, 
they flow on diminishing gradients. Because of this, their velocity 
and therefore their erosive power decrease constantly. In other 
words, an area approaches base-level more and more slowly the 
nearer it gets to it, and it may take as long to wear away the last 
few feet above base-level as it did all the other hundreds or thousands 




Fig. 139. A monadnock on a peneplain. Tower, Minnesota. (Mead.) 

of feet that once lay above. Few, if any, areas have been absolute- 
ly base-leveled. The time required is enormous, and before the 
task is completed, an area is likely to be elevated with reference 
to sea-level, and the quickened rivers started upon the task of again 
reducing the elevated land to base-level. But many areas have 
been nearly base-leveled. Such plains are peneplains (almost plains) . 
Above their otherwise nearly level surface, occasional elevations may 
rise abruptly. These elevations, known as monadnocks (Fig. 139), 
owe their existence to (1) the greater resistance of their rocks, or 
(2) a favorable position among drainage lines. The time required 
for reducing a drainage basin to a base-level plain is a cycle of erosion. 
As implied above, cycles of erosion commonly are brought to an 
end by relative uplift of the land before they are completed. 

The terms youth, maturity, and old age, as used in geography, 
apply to stages of development, and not to periods of years. Thus 
a small river, working on soft material, may bring its valley to old 
age in less time than that required for a large stream, opposed by 
resistant rocks, to bring its valley to maturity. 



228 MODIFICATION OF LAND SURFACES 

Influence of stage of erosion on human activities. The den- 
sity of population of a region and the condition and activities of 
its people are influenced greatly by the stage which it has reached 
in its topographic development. Many young rivers are inter- 
rupted by falls and rapids (p. 230) which afford water power for 
manufacturing, but interrupt or prevent navigation. Many young 
rivers, too, are not available for commerce partly because they 
flow in narrow valleys, far below the level of the surrounding coun- 
try. In parts of western United States, it is also impracticable to lift 
the waters of such streams to the neighboring uplands for purposes 
of irrigation. Thus the waters of the Colorado River can be used 
for irrigation only in the upper part of the river system, or below 
the Grand Canyon, and the larger irrigation projects of southern 
Idaho are related definitely to breaks in the walls of the deep canyon 
of the Snake River. Again, very deep valleys may make travel 
across their courses almost impossible. In such cases, places where 
the valleys can be crossed may have all the importance of mountain 
passes, controlling the courses of trails and roads. The Denver and 
Rio Grande Railroad crosses the Green River in eastern Utah where 
there is a gap in the canyon wall, a gap that earlier fixed the course 
of the Spanish Trail. Roads may run in any direction over young 
plains whose valleys are shallow. Nearly all the land of such plains 
can be farmed, so far as topography is concerned. The poorly 
drained inter-stream flats may require ditching or tile draining, 
however, as in parts of Iowa and Illinois. 

Where relief is great, early maturity is least favorable to most 
human activities. The larger rivers may be navigable, but most of 
their tributaries are likely to have steep gradients, with falls and 
rapids. At this stage, run-off is at a maximum, and streams are most 
subject to floods. Many of the larger rivers are crossed at ferries 
and fords, for bridges are hard to maintain. Good sites for river towns 
may be few. Wagon roads and railroads follow the narrow ridges 
between the valleys, or the flats of the larger streams. Farming is 
difficult on the steep valley slopes, where soils are likely to be thin 
and easily washed away. In general, the population of such regions 
is sparse and non-progressive, having little contact with the outside 
world. Mineral deposits or other special resources may create in- 
dustrial centers, whose progress serves to emphasize the backward- 
ness of the region as a whole. These conditions are illustrated in 
parts of the Cumberland and Alleghany plateaus (p. 173). 



STAGE OF EROSION AND HUMAN ACTIVITIES 229 

Old rivers are, as a rule, free from rapids and falls, and in most 
cases have gradients so gentle that they do not afford good water 
power. While these conditions favor navigation, the latter may 
be interfered with by sand bars (p. 237) and the shifting and crooked 
courses of the channels. Much of the land of the broad flood-plains 
of old rivers is swampy and of little use until drained, but is then of 




Fig. 140. The canyon of the Yellowstone. (Hillers, U. S. Geol. Surv.) 



great fertility (Why?). While floods are most numerous in valleys 
whose slopes are steep, they are more likely to be disastrous to prop- 
erty on the broad, low flats of older rivers, such as the lower Mississippi 
(P* 2 37)« On the gentle inter- valley slopes of an old area, the soils 
are likely to be deep (Why?); their fertility depends chiefly on the 
character of the underlying rock. The area of land which can be 
farmed is, as a rule, much greater in topographic old age than in ma- 
turity. On peneplains, as on youthful plains of low relief, travel is 
easy in all directions. Wagon roads and railroads are not confined 
to certain courses by topography. 



230 



MODIFICATION OF LAND SURFACES 



Canyons and gorges. Valleys which are narrow and deep 
often are called gorges if small, and canyons if large. The Colorado 
Canyon is the greatest canyon known. Its depth is about a mile, and 
it is eight to ten miles wide at the top. Its sides are step-like, because 
of the unequal hardness of the rock of the canyon walls. The harder 
strata are the cliff-makers. The Yellowstone (Fig. 140), Snake, and 
Columbia rivers have wonderful canyons in some parts of their 
courses, and so has the Arkansas River where it flows through the 

Rocky Mountains. 
The canyons of many 
smaller and less well- 
known rivers are al- 
most equally striking. 

A narrow valley means 
that the processes which 
have made it deep have 
outrun the processes tend- 
ing to make it wide. Val- 
leys are deepened rapidly 
when their gradients are 
high and their streams 
strong. They are widened 
slowly (1) when the climate 
is arid, so that there is little 
slope wash, (2) when the stream is so swift that it does not meander, and (3) when 
the material of the sides is such that it will stand with steep slopes. Therefore 
(1) great "altitude, (2) arid climate, (3) swift streams, and (4) rock which will 
stand in steep slopes, favor the making of canyons. In other words, young 
valleys in plateaus and mountains (as in western United States) are likely to be 
canyons. (How can there be large, strong streams in dry regions?) 

Some of the ancient cliff-dwellers made their homes in the recesses of canyon 
walls (Fig. 141), probably because these positions could be defended easily. 

Canyons must change into valleys of another type, for the stream 
in the canyon will in time cut down to its base-level. The valley 
will then stop growing deeper, but widening will still go on, and the 
narrow valley will become so wide that it will cease to be a canyon. 

Rapids and falls. The bed of a stream may be steeper at some 
points than at others, and there the stream flows more rapidly. The 
quickened flow constitutes a rapids; or, if the water in a stream's bed 
drops over a cliff, it makes a waterfall (Fig. 142). Waterfalls and 
rapids are important chiefly because they render the power of the 
streams available to man for purposes of manufacturing, lighting, 




Cliff dwellings, southwestern Colorado. 



RAPIDS AND FALLS 



231 



transportation, etc. (p. 288). Many electric railroads and many 
industries depend for power on electricity developed by falls and 
rapids, and railroads and fac- 
tories of all sorts are likely to 
depend on this sort of power 
still more largely in the future. 
Rapids and falls interfere with 
navigation, or prevent it alto- 
gether (p. 228). 

Waterfalls come into existence in 
various ways. A river flowing on the 
high gradient shown in Fig. 143 is 
likely to be an eroding river. It will 
wear its channel faster at A , where the 
rocks are soft, than just above, where 
they are hard, with the result shown 
in Fig. 144. The continued wear of 
the water in such a case would cause 
the rapids at A (Fig. 144) to become 
steeper, and in time the descending 
water would become a fall (Fig. 145). 
In this case, the rapids and falls de- 
pend on inequalities of hardness in the 
bed of the stream. This is a common 
way in which falls and rapids origi- 
nate. A landslide or lava flow may 
form a dam, over which the water 
falls or flows in rapids. Most of the 
waterfalls of the United States are 
due to glaciation (pp. 256, 265). 

Falls and rapids are undergoing 
constant change, although the change 
is usually very slow. Many falls are 
moving slowly up-stream, because the 
water undermines the hard layer of 
rock over which it drops (Fig. 145). 
As a fall moves up-stream, it becomes 
lower in many cases (Fig. 145). It is 
clear that such falls will disappear if 
they recede far enough. If the hard 

rock over which the water drops is in the position shown in Fig. 146, the fall 
will not recede, though it will become lower, and will disappear when the stream 
cuts down to base-level, where the fall is. (What would be the effect of re-eleva- 
tion of the basin?) Rapids and falls are temporary features of streams, and, like 
canyons, are marks of youth. In time, therefore, all existing rapids and water- 
falls will disappear. 




Fig. 142. Falls of the Black River, 
Wisconsin. (Smith, Wis. Geol. Surv.) 



232 



MODIFICATION OF LAND SURFACES 



Narrows. Many valleys are narrow where they cross a tilted 
layer of hard rock. Such a place in a valley is a narrows, or water- 
gap (Fig. 147). The Delaware Water-Gap through Kittatinny 
Mountain (Pa.-N. J.) is a well-known example. 




Fig. 145. 



Figs. 143, 144, i45 
of a waterfall. 



Diagrams to illustrate the development and extinction • 
Why will the waterfall cease to retreat up-stream when it reaches C-B, Fij . 



145? What changes will occur after it reaches this placer 



Narrows sometimes serve as gateways through mountains, and so control lines 
of travel. The narrows of Wills Creek in Wills Mountain, Maryland, may serve 
as an example. In the early days of American history, Fort Cumberland was 
built at this narrows to guard the important pass through the mountains, and 
Washington's and Braddock's roads ran west through it. At the present time, the 
Cumberland National Road (Fig. 215) and an important railway make use of it. 



PIRACY AMONG RIVERS 



233 



Accidents to streams. Streams are subject to many accidents. 
If the land through which they flow sinks so that its slope is reduced, 
they flow less rapidly, or may even cease 
to flow. If the lower end of a valley 
sinks below sea-level, the sea-water 
enters and forms a bay, drowning the 
lower end of the river and its valley. 
If the streams along a coast end in 
bays, we infer that the coast has sunk, 
and that its rivers and valleys have 
been drowned. Thus Delaware Bay and 
Chesapeake Bay are drowned valleys. 
If the basin of an old stream is raised so that the gradient of the 
stream becomes greater, its velocity is increased, and it again takes 
on the character of youth. Such streams are said to be rejuvenated. 




Fig. 146. Diagram of water- 
falls developed on vertical beds. 




Fig. 147. Lower Narrows of the Baraboo River, Wisconsin. The valley- 
widens beyond the gap, the same as in the foreground. 



If by headward growth one valley reaches and enters another 
where the latter is at a higher level, it may steal the water which other- 
wise would flow down the higher 
valley (Figs. 148 and 149). The 
stream which steals is a pirate. 
The stream stolen is diverted, and 
the stream which has lost its upper 
water is beheaded. Piracy has been 
rather common among rivers, espe- 
cially in mountain regions. In the 
Figs. 148, 149. Diagrams to Appalachian region, for example, 
illustrate stream piracy. there are few large streams which 




234 



MODIFICATION OF LAND SURFACES 



have not either increased their waters by piracy, or suffered loss by 
the piracy of others. Piracy is favored by inequalities of hardness, 
for streams which do not cross hard rock deepen their channels 
more readily than those which do (Fig. 150). 

When a stream is diverted from a narrows, the water-gap becomes 
a wind-gap. Wind-gaps are common in most mountain regions 
which have advanced to late maturity. Cumberland Gap, in the 
southeastern corner of Kentucky, is an example. It afforded many 




Fig. 150. A case of stream piracy in Pennsylvania. The upper part of the 
present Wiconisco Creek formerly was tributary to Deep Creek, joining the latter 
at "A." (From Millersburg and Lykens, Pennsylvania, Sheets, U. S. Geol. Surv.) 

What enabled Wiconisco Creek to behead Deep Creek? What was the prob- 
able origin of the mountain gap at "B'7 Is future piracy likely to occur in this 
region? Why? 

of the early emigrants the best route across the mountains, and during 
the last quarter of the eighteenth century probably more than 300,000 
people passed through it to settle in the West. The many wind-gaps 
of the Blue Ridge Mountains were important in the early westward 
movement of population, and again in the campaigns of the Civil War. 



DEPOSITION BY STREAMS 

Causes of deposition. Streams may become overloaded in 
various ways, and so be forced to deposit their excess sediment: 
(1) Their carrying power may be reduced by a decrease of gradient. 
The change may take place suddenly, as at the base of a steep slope, 
or it may take place slowly, as a stream flows through a valley whose 
slope becomes gradually less. (2) Their carrying power may be 



WHY STREAMS DEPOSIT 



235 



diminished by decrease of volume. Streams flowing through arid 
regions may receive little water, and lose much by evaporation and 
by soaking into the dry earth. Many streams in the West leave 
the mountains bank-full, to wither and disappear on the lower lands. 
Many also have much of their water withdrawn for purposes of 
irrigation. (3) Tributary streams with high gradients may bring 
to the main streams more sediment than the latter can carry away. 



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Fig. 151. Alluvial fan at the mouth of Aztec Gulch, southwestern Colorado. 
(U. S. Geol. Surv.) 



(4) Many rivers deposit at their mouths, where the current is 
checked. 

Deposits at the bases of steep slopes. Every shower washes 
fine sediment down the slopes of hills and mountains, and much of 
it is left at their bases, where the velocity of the water is checked 
suddenly. At the lower end of every new-made gully on a hillside, 
there is a mass of debris which was washed out of the gully itself 
(Fig. 127). Material in such positions accumulates in the form 
of an alluvial cone, or a gentler sloping alluvial fan (Fig. 151). The 
rivers descending from the Sierras to the valley of California have 
built great fans along the foot of the range, and most of the rivers 
coming out of the Rockies to the plains east of them have done the 



236 



MODIFICATION OF LAND SURFACES 



same thing. Many of the fans of streams descending from the west- 
ern mountains are miles across. Fans made by neighboring streams 
may grow until they unite to form a compound alluvial Jan, or a pied- 
mont alluvial plain. Such plains exist at the bases of many mountain 
ranges. Their alluvial deposits may be hundreds of feet thick. 

Many alluvial fans and piedmont alluvial plains are valuable 
for farming. (In general, which would be more valuable, the higher 




Fig. 152. Cultivated alluvial fan near Riverside, California. 



or the lower portions of alluvial fans? Why?) In parts of southern 
California, for example, such lands are so valuable that farms are 
very small and highly improved (Fig. 152). Water is supplied (1) 
by wells, through which the fan is made to yield up the water it has 
absorbed, or (2) by irrigating ditches which connect with a stream 
or reservoir at a greater height. Many villages in mountain valleys 
are situated on alluvial fans. The agricultural settlements of Utah 
spread southward from the vicinity of Great Salt Lake along the 
piedmont alluvial plain at the west base of the Wasatch Mountains. 
Most of the cities and villages of the state are within this belt. 

Deposits in valley bottoms; flood-plains and man. The 
gradient of a stream generally becomes less toward its mouth, and 






FLOOD-PLAINS AND MAN 



237 




so it happens that sediment is spread for great distances along valley 
bottoms. Some of it is left in the channels, and some is spread over 
the low lands along the streams, making alluvial plains. 

Streams sometimes deposit sand bars in their channels, especially in low 
water. Bars, and the tree trunks and snags which they often catch and hold, 
hinder navigation, especially when rivers are low. In earlier years, many steam- 
boats were wrecked by such obstructions in the Missouri and Mississippi rivers. 
Later, large sums of money were spent in removing snags and dredging channels. 

Alluvial plains along large rivers are almost flat, though they 
slope gently down-stream, and many of them have natural levees. 
This term is applied to the low ridges along the banks of the channel 
(Fig. 153). In times of flood, the current in the main channel is 
swift; but so soon as 
the water spreads be- 
yond its channel, its 
velocity is checked be- 
cause its depth sud- 
denly becomes less, and 
it promptly abandons 
much of its load. Dur- 
ing the period of over- 
flow, the edges of the channel current are checked by the slower 
moving flood-plain water, and this causes further deposition on the 
banks of the channel. Repeated deposition in this position gives rise 
to levees. Embankments have been built by man upon the natural 
levees of some rivers to prevent the flooding of the valley flats, and to 
permit the settlement of the bottom lands. Louisiana alone has spent 
more than $35,000,000 since 1865 in levee building, and is expending 
now about $800,000 a year in this way. (Why must the protective 
levees be built higher and higher as time passes?) In spite of such 
improvements, floods are unfortunately frequent. The damage 
which they did to buildings, bridges (Figs. 154 and 155), railroads, 
etc., in the United States in 1908 was estimated at more than $237,- 
000,000, though not all this damage was done on the flood-plains of 
large rivers. Impressive as this estimate is, it takes no account of 
the great damage done to the land itself, nor is it possible to measure 
the suffering and reduced efficiency of the people living where there 
have been great floods. 

In early days, most of the people in Louisiana and Mississippi 
lived in narrow belts along the levees of the Mississippi and its 



Fig. 153. Diagram showing natural levees. 



238 MODIFICATION OF LAND SURFACES 




Fig. 154. Railway bridge over the Nolichucky River at Unaka Springs, 
Tennessee. (From photograph by Glenn, U. S. Geol. Surv.) 




Fig. 155. Same place as shown in Fig. 154 after the bridge and piers were swept 
away by the flood of May, iqoi. (From photograph by Glenn, U. S. Geol. Surv.) 



TOWN SITES AND RIVERS 



239 




Fig. 156. The Rio Grande near Browns- 
ville, Texas. 



branches. The land here was high enough and dry enough to be 
farmed, very fertile, and close to the streams which were the great 
highways of that time. The plantations were narrow along the 
streams, and extended back, at right angles to them, until the land 

became too low and wet to 

cultivate. 

A stream in an alluvial plain 
is likely to wind about, or 
meander (Fig. 156). This is the 
result of the low velocity of 
such a stream, for sluggish 
streams are turned aside easily. 
Were such a stream made 
straight, it would become 
crooked again, for the banks 

of all streams are less firm at some places than at others, and the 
stream would cut more at those places. Once started, meanders tend 
to become more and more pronounced (Fig. 157) until, probably in 
some time of flood, the stream cuts through the neck of the meander 
and straightens its course. When a stream has cut off a meander, 
the abandoned part of the channel may remain for a time unfilled 
with sediment. If it contains standing water, it becomes the site 
of an oxbow lake or bayou (Fig. 156). 

In meandering, a stream sometimes reaches and undermines the 
valley bluff, thus widening its valley flat. This is, indeed, the most 
important process in the widening of 
valley flats (p. 223). Towns grew up 
early on the bluffs of the lower Missis- 
sippi at points where the river touched 
the side of its valley. In this way the 
location of Natchez, Vicksburg, Mem- 
phis, and other places was determined. 
Such sites, overlooking and controlling 
the river, were bones of contention 
between Spain and the United States during the dispute over 
the southwestern boundary, from 1783 to 1795. The same physio- 
graphic features located the Confederate defenses in the Civil War 
at Columbus (Ky.), Ft. Pillow (Tenn.), Vicksburg (Miss.), Grand 
Gulf (Miss.), and Port Hudson (La.). 

By shifting their courses, as the result of deposition and meander- 




Fig. 157. Diagram showing 
development of a meander. 



240 



MODIFICATION OF LAND SURFACES 



ing, streams have affected human interests in many other ways. Vil- 
lages which grew up on the banks of navigable rivers because oi 
the river trade, in some cases have been left far from the streams 
by changes in the positions of the latter. Such villages usually 
decline when the streams withdraw their patronage. Other places 
built on river banks have been preserved at great expense, while 
some have been washed away. The Mississippi River flows over 
the site of Kaskaskia, one of the most important French settle- 




Fig. 158. A delta in a lake in Switzerland. (From photograph by Robin.) 



ments in the upper Mississippi Valley, and the first capital of 
Illinois. The Missouri River destroyed Franklin, Missouri, an 
outfitting place in the 1820 's for the trade across the Great Plains 
to Santa Fe. 

Many streams have been used as boundaries between counties and states. 
In numerous cases the shifting of the stream has led to boundary disputes, for, by 
the cutting off of meanders, tracts of land have been shifted from one state to 
another. In the case of the Missouri River, there have been disputes between 
Nebraska and South Dakota, Nebraska and Iowa, and Nebraska and Missouri. 
The Supreme Court finally decided that when the Missouri develops a cut-off, the 
boundary line does not shift with the river, but remains where it was. Again, 
many boundaries have been defined as following the "main channels" of streams. 
Where there are several channels, which is the case in many rivers, the question may 
arise as to which one is the main channel. Furthermore, the main channel at one 
time may be a subordinate channel at another time. These conditions have led to 
disputes over the ownership of islands in different rivers. 

The objections to rivers as boundaries are most serious where they form inter- 
national boundaries. Thus the shifting of the Rio Grande makes it a poor bound- 
ary between the United States and Mexico. In addition, so much water was taken 
from the Rio Grande for irrigation in southern Colorado and New Mexico that 
there was little water for Mexican farmers below El Paso. Mexico protested to 
the United States, and finally it was arranged that the United States should build 



DELTAS AND THEIR RELATIONS TO MAN 241 

a great reservoir on the Rio Grande north of El Paso, to store the water of the river, 
and that Mexico should receive a certain fixed amount of water from this reservoir 
each year. 

Most flood-plains are very fertile, but many are too wet to be 
cultivated without drainage. About one-sixth of Arkansas, for ex- 
ample, is swampy, but most of its swamp area is rich alluvial land. 
When drained, the wet lands of the United States will form one of the 
greatest resources of the nation (p. 300). 

Deltas and their relations to man. Where a stream flows 
into the sea, or into a lake, its current is checked promptly, and 







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Fig. 159. The lower part of the delta of the Mississippi River. 



soon stopped entirely. Its load therefore is dropped, and if not 
washed away by waves and currents, makes a delta (Fig. 158). That 
part of a delta above the surface of the water in which it is built 
is like a nearly flat alluvial fan. Deltas may be built where one stream 
flows into another, especially where a swift stream with much sedi- 
ment joins a slow one. 

Much land has been made by the growth of deltas. Thus the 
Colorado River has built a great delta across the Gulf of California 
near its former upper end. In the arid climate of the region, the shut- 
off head became a nearly dry basin, the lowest part of which is about 
300 feet below sea-level. The soil being good, water alone was needed 



242 



MODIFICATION OF LAND SURFACES 




Fig. 160. Delta of the Nile 
River. The dotted area is 
desert. 



to make this area fertile, and the results that have followed the 
irrigation of parts of it. justify its new name, the "Imperial Valley." 
Figs, dates, and other tropical products grow here luxuriantly. The 
deltas of the Mississippi (Fig. 159), the Nile (Fig. 160), and the 

Hwang-ho (Fig. 161) rivers are among 
the large and well-known ones. The 
delta of the Ganges and Brahmaputra 
has an area (above water) of some 
50,000 square miles (nearly as large as 
Illinois). 

While rivers have made much delta 
land, it is to be remembered that the 
material of which they are composed has 
been removed from vastly larger areas, 
and that much of it was rich soil. It is 
probable that the loss to man through 
the removal of such material is far greater than the gain resulting 
from its deposition. 

The surfaces of most deltas are nearly fiat, and the streams which cross them 
often give off branches, called distributaries, which flow independently to the edge 
of the delta, and are subject to frequent changes. These changes sometimes affect 

commerce in a vital way (p. 351). 
The distributaries of the Mississippi 
offered the English in the War of 181 2, 
and the Federals in 1862, several pos- 
sible lines of approach to the vicinity 
of New Orleans. The necessity of 
watching these different lines scat- 
tered the men and the resources, and 
weakened the resistance of the de- 
fenders of the city. By cutting the 
levees and flooding the lower land, 
General Jackson was able to increase 
greatly the difficulties of the English. 




J) el la of the Hwang-ho. 



Most delta land away from 
natural levees is low and wet, 
and must be diked and drained 



before it can be farmed. The soil of great deltas is deep (What 
determines its thickness?), and in most cases rich in the mineral 
elements of plant food. Some deltas, like that of the Hwang-ho, 
support dense populations. Delta lands are, however, subject to 
disastrous floods. It is estimated that the flood of the Hwang-ho 



ALLUVIAL TERRACES 243 

River in September, 1887, drowned more than a million people and 
caused the death of many more by disease and famine afterward. 

Previous to 1853, the Hwang-ho had flowed for many years into the Yellow 
Sea south of the Shan-tung promontory (Fig. 161). In that year, it shifted its course 
in flood time, forming a new channel leading northeast into the Gulf of Pechili, 300 
miles north of its former mouth. Other changes at earlier times, running as far 
back as 2293 b. c, are recorded in the annals of Chinese history. 

Lakes exist on many large deltas. Some are former sections of the 
shifting streams, and some (Fig. 159) are portions of the sea or lake 
in which the delta is built, portions that were surrounded by the 
deposits or shut in between them and the former shore-line. 

Delta cities have peculiar problems, as illustrated by New Orleans. For a 
long time, floods were of almost yearly occurrence. In 1849, for example, 220 in- 
habited squares were flooded and 12,000 people were driven from their homes. 
Street improvement was difficult; there were no paving stones save those brought 
as ballast in ships. As late as 1835, only two streets were paved for any consider- 
able distance. On the other streets, carriages in wet weather sank to the axle in 
mire. The question of a domestic water supply was an early and pressing one, 
and for a long time the practice was general of building cisterns to catch the rain- 
water. The city could not easily empty its sewage into the Mississippi, for the 
banks of the river are above the houses. Under these conditions, the city was 
for years a very unhealthful place. In recent years these disadvantages have 
been largely overcome. New Orleans now pumps its sewage into the river, 
cisterns are condemned, many streets are well paved, and the city is much more 
healthful than formerly. 

Alluvial terraces. When a river which has an alluvial flat is reju- 
venated (p. 233), the stream sinks its channel below the level of the flat. 
The remnants of the old flood-plain are then alluvial terraces (Fig. 162). 
Such terraces are also formed in other ways. Thus if a stream is sup- 
plied for a time with an excess of load, it aggrades (builds up) its valley. 
If, later, the excess of sediment ceases, the stream sets to work to re- 
move that which was temporarily laid aside in its flood-plain. 

The material of many alluvial terraces is gravelly or sandy, 
and their soils vary greatly in value. Many towns and cities are 
built on alluvial terraces. (What advantages would such locations 
have over sites on flood-plains? On the edges of valley bluffs?) 
The leading towns of the Platte Valley in Nebraska are on terraces 
near the mouths of tributary valleys. (Of what significance is the 
last fact?) In the middle Illinois Valley, every town is on a terrace, 
and every terrace has a town. Terrace sites were chosen for most of 
the first settlements of the Connecticut Valley, such as Hartford, 
Weathersfield, and Windsor. 



244 



MODIFICATION OF LAND SURFACES 



Summary. From the physiographic standpoint, the mission of 
running water is to wear the land to base-level. The material it 




Fig. 162. Terrace of the Columbia River. (Willis.) 

carries toward and to the sea is prepared for transportation largely by 
the agents of weathering, and in subordinate amount is worn from the 
solid rocks by the streams themselves. The irregular wearing down 




163, [64. Drainage maps of contrasted areas of equal size. 

of the land produces most of the familiar relief features of the surface. 
Their characteristics are determined by several factors, especially 



QUESTIONS 



245 



by the character and position of the rocks from which they were 
carved, and the stage of development which they have reached. On 
its way to the sea, the waste of the land is often laid aside by over- 
loaded streams, forming topographic features subject to later destruc- 
tion by eroding waters or by other agencies. All phases of river work 
affect human interests vitally. Much can be done by regulating and 
controlling streams to increase 
their 



prevent 




usefulness and 
their doing damage. 

QUESTIONS 

i. In what parts of the United 
States would a valley need to be deep 
to have a permanent stream? 

2. What are all the conditions 
which may help to make the flow of 
streams (i) regular, and (2) irregular? 

3. Why do streams carry more 
and coarser material during floods 
than at other times? 

4. Is the bed of the upper St. 
Lawrence River being eroded much? 
Why? 

5. (1) Why is the rate of erosion 
in the Colorado Basin so rapid (Fig. 
126), especially in view of the fact 
that a large part of it is in an arid 
region? (2) Why is the rate in the 
basin of the Red River of the North 
relatively so slow (Fig. 126)? 

6. Why are steep slopes charac- 
teristic of arid climates? 

7. What is the age, in terms of 
erosion, of the area shown in Fig. 80? 

8. (1) Interpret the contrasted 
drainage shown by Figs. 163 and 164. 

(2) In what stage of erosion is the area shown by Fig. 163? (3) Does Fig. 164 
indicate the stage of erosion which that area has reached? Why? 

9. (1) What topographic features are shown in Fig. 165? (2) Compare 
and contrast the northern and southern parts of the area as to (a) the climate, 
(b) the character of the rocks, and (c) the work of the streams. 

10. In general, what stream-built features are (1) most, and (2) least endur- 
ing? Why? 

11. State all the important ways in which (1) stream erosion and (2) stream 
deposition affect human interests. 



Fig. 165. 



246 MODIFICATION OF LAND SURFACES 

The Work of Ice 

Snow is perhaps the most common form of ice, but ice on ponds, 
lakes, and rivers is familiar to all who live where winters are cold. 
In middle latitudes the water in the soil and rocks freezes in winter, 
often to a depth of several feet. In some parts of the world, too, there 
are glaciers. In most of its forms ice has some effect on the surface 
of the land. 

Ice on lakes and rivers. Most lakes and rivers in middle lati- 
tudes are frozen over for several months each year. This is in some 
cases a great disadvantage from the standpoint of commerce. The 
upper Mississippi River is closed to navigation for more than four 
months of the year. The open season on the upper Great Lakes lasts 
about seven months. The St. Lawrence River is closed by ice about 
five months each year, and is difficult to enter during another month. 
Hudson Bay and its tributary rivers are closed even longer. It 
was a great disadvantage to the French colonies of interior Canada 
that they were shut off completely from the mother country .for 
nearly half the year, and it is a serious disadvantage to Canada to- 
day that her two main gateways from the Atlantic Ocean are closed 
so much of the time. The inland waterways of England and France 
are open throughout normal years; those of Germany and central 
Russia are closed more often, and for longer periods the farther they 
are from the Atlantic. Those of northern Russia are closed for five 
or six months. (Why are the waterways of western Europe so in 
contrast with those of North America in corresponding latitudes?) 

In some cases, the ice of rivers and lakes serves a good purpose. 
Fishing villages formerly were built on the ice in such places as Sagi- 
naw Bay, Michigan, and are still common in the gulfs of Bothnia and 
Finland. When frozen over, many northern rivers serve as roadways 
for local business. The cutting and packing of ice for sale during 
the following summer is an important industry on many lakes and 
rivers in northern United States. 

Ice on the sea. In high latitudes ice forms on the sea where 
the water is shallow, and in polar regions it becomes several feet 
deep, even on the open sea. Sea-ice is broken up in the summer, 
and t he floating pieces are called floe-ice. When the floes are crowded 
together, they make ice-packs, some of which are hundreds of miles 
5. Ice-packs arc obstacles to polar navigation, and make most 
of the north coast of Russia and Siberia useless even in summer. 



FORMATION OF GLACIERS 



247 



The closing of ocean harbors and of seas connected with the 
ocean, like the closing of inland waters, is a great hindrance to com- 
merce. The North Sea has a tremendous advantage over the Baltic 
in this regard. The shores of the latter are hampered by ice each 
winter, while those of the former are edged with ice only during the 
most severe weather. The key to Russian expansion since the days 
of Peter the Great has been the attempt to secure ice-free harbors. 



EXISTING GLACIERS 

General 
Conditions for glaciers. Where it is so cold that snow lasts from 
year to year over any considerable area, the snow constitutes a snow- 
field (Fig. 1 66) . Snow-fields occur in mountains in nearly all latitudes, 
and in polar regions even down to sea-level. Where snow accumulates 




Fig. 166. Snow-fields in Alaska. Russell Fiord at right of view. (Brabazon, 
Canadian Boundary Commission.) 

to great depths and lies long on the surface, it changes to compact 
ice, and becomes an ice-field. The beginning of this change is distinct 
in banks of snow which last for some weeks. Such banks are made up of 
coarse granules of ice, sometimes as large as peas. The change from 
flakes of snow to granules of ice is due, in part, to the melting of the 
snow and the re-freezing of the water. If there is much snow, it is 
compressed by its own weight, and after being compacted in this way, 
the freezing of the sinking water binds the granules together. When 
the amount of ice made from snow becomes great enough, it moves 
out slowly from the place where it was formed to lower and warmer 
places. When it begins to move, it becomes a glacier. 



248 



MODIFICATION OF LAND SURFACES 



Functions of glaciers, (i) One mission of glaciers is to return to 
lower and warmer levels moisture which otherwise would be locked up 
indefinitely as snow and ice. (2) Like rivers, glaciers wear the land 
and move the resulting waste toward the sea. (3) Long after glaciers 




it o Fi /v 167. A valley glacier in the Cascade Mountains, Washington. (Willis, 
U. S. Geol. Surv.) 

have melted away, some of their effects on the conditions of life remain, 
because of the changes they made in topography, soil, and drainage. 
Thus past glaciation is a leading factor in the geography of northern 
United States and northern Europe. (4) Glaciers tend to maintain a 
relatively uniform volume in the streams which flow from them, and in 
various mountain regions such streams afford great amounts of power. 



TYPES OF GLACIERS 



249 



Types of glaciers. Glaciers have various forms, depending 
on the amount of ice and on the shape of the surface beneath and 
around them. If the snow-field which gives rise to a glacier is 
at the upper end of a mountain valley, the ice moves down the valley 
as a valley glacier (Fig. 167). In high latitudes, snow-fields and 
ice-fields may lie on plains or plateaus. When the ice in such situ- 
ations begins to spread, it 
moves in all directions from its 
center. Such glaciers are ice- 
caps or ice-sheets. Very large 
ice-caps sometimes are called 
continental glaciers. The main 
ice-caps of Antarctica and 
Greenland (Fig. 168) are large, 
but small ones are found on 
various promontories along the 
coast of Greenland, on Iceland, 
and on some other Arctic islands. 
Glaciers occur also at the bases 
of some mountains, being 
formed by the union of the 
spreading ends of valley gla- 
ciers. Such glaciers are pied- 
mont glaciers. Of these types, 
valley glaciers are most com- 
mon and most familiar, but the 
large ice-caps contain much 
more ice. 




Map of Greenland ice-cap. 



Valley Glaciers 
Distribution. The chief re- Fi< 
gions of valley glaciers are the 
high mountains of Eurasia, the southern Andes, and the higher moun- 
tains of northwestern United States and western Canada. In Alaska, 
high mountains near the coast receive abundant precipitation from 
the ocean winds. The heavy snowfall on the upper slopes feeds many 
glaciers, some of which reach the sea. 

The glaciers of Switzerland are known best and help to attract thousands of 
tourists to that country each year. In 1910, Congress created Glacier National 
Park on the Continental Divide in northwestern Montana (Fig. 224). It is about 



2 5 o MODIFICATION OF LAND SURFACES 

sixty miles in length and contains more than sixty glaciers. This may become one 
of the best known and most visited of our National Parks, for the mountains and 
glaciers offer the chance for mountaineering of real Alpine character, the streams 
abound in trout, and the mountains still shelter enough game animals to become 
an important game refuge. The park contains one of the most beautiful portions 
of the Rocky Mountains lying within the United States. 

Size. There are nearly 2,000 glaciers in the Alps, only one 
of which has a length of ten miles. Less than 40 have a length 
of five miles, while the great majority are less than one mile long. 
Only a few are so much as a mile wide, and none are more than a 
few hundred feet thick. Larger glaciers occur in the Caucasus 
Mountains and in Alaska. Seward Glacier in Alaska is more than 
50 miles long, and is three miles wide at the narrowest place. The 
glaciers of western United States south of Alaska are not so large 
as the larger glaciers of the Alps. 

Movement. The ice of a glacier is wasting all the time, both 
by melting and evaporation. In spite of this, many glaciers remain 
about the same size year after year. This is because the loss by 
melting is replaced by advance from the snow-fields, from which the 
ice creeps down the valleys until it reaches a place so warm that the 
melting at the end balances the forward motion. Most glaciers move 
very slowly. Of those whose rate of advance has been measured, 
few move more than two feet a day, and very few as much as seven. 

The rate of movement depends chiefly on (1) the thickness of the moving ice, 
(2) the slope of the surface over which it moves, (3) the slope of the upper surface 
of the ice, and (4) the topography of its bed. (What combination of conditions 
would favor most rapid movement?) The exact nature of glacier movement is a 
disputed question. It was thought formerly that glaciers flowed somewhat as 
stiff liquids do, but it is very doubtful if the motion is really flowage. 

Ice-Caps 

As already stated, ice-caps may lie on plains or plateaus, and 
may be large or small. 

Greenland has an area of 400,000 to 600,000 square miles, and all but 
its borders is buried beneath one vast field of ice and snow (Fig. 168). 
Except on a narrow border of a mile or so at the edge of the ice-sheet, 
not even a bowlder or a pebble interrupts the great expanse of white. 

The thickness of the Greenland ice is not known, but, where 
thickest, it is probably thousands of feet. Near its margin the 
ice is much crevassed, but the interior is fairly smooth so far as known. 
The ice of this great field is creeping slowly outward. The rate of 




THE POLAR ICE-CAPS 251 

movement never has been measured, and is probably not the same 
at all points, but it has been estimated not to exceed a foot a week. 
This ice-cap is, in one sense, more of a desert than the Sahara, since 
it is inhabited even less than the latter. 

Where the edge of the Greenland ice-cap lies a few miles back from 
the coast, the rock plateau outside it has many valleys leading down 
to the sea. Where the edge of the ice-cap reaches the heads of these 
valleys, ice moves down them, 
making valley glaciers. Many 
of the latter reach the sea, 
where their ends are broken off 
and float away as icebergs. 
This is the source of most of 
the bergs (Fig. 169) seen from 
steamers which cross the North Fig. 169. An iceberg. 

Atlantic. Some are so large 

that they float far to the south before they are melted. Since they 
are sometimes surrounded by fog, they are a menace to ships (p. 149). 

The Antarctic snow-and-ice-cap is much larger than that of 
Greenland, but its area is not so well known. It is probably several 
million square miles in extent, and the thickness* of its ice probably 
exceeds that of Greenland. The ice descends to the sea at many 
points, and huge blocks of it become icebergs. 

Piedmont Glaciers 
A number of alpine glaciers come down adjacent valleys in the 
St. Elias range of Alaska, and spread out on a low plain at its base. 
So much do their ends spread that they unite to form a single body 
of ice, 70 miles long and 20 to 25 miles wide, called the Malaspina 
Glacier. Its area is greater than that of Delaware. Its central 
portion is free from debris, but has thousands of deep, wide cracks. 
A belt along the margin of the glacier .five miles or less in width is 
covered by rocky and earthy debris, and parts of it are clothed with 
vegetation. The undergrowth is here so thick that travelers have to 
cut paths, and on the edge of the ice there are trees three feet in diam- 
eter. Other glaciers of the same type occur about North Greenland. 

ANCIENT GLACIERS 

There have been times when glaciers were much more extensive 
than now, for various features produced only by glaciation (pp. 255- 



252 



MODIFICATION OF LAND SURFACES 



265) are found in many places now free from ice. The latest of these 
periods is known as the Glacial Period. In this country, glaciers 
existed even in the mountains of New Mexico, Arizona, and Nevada. 




Fig. 170. Sketch-map showing the area in North America covered by ice at 
the stage of maximum glaciation. (Chamberlin.) 

The amount of ice in the glaciers of Utah or Colorado was then 
far greater than all that now exists in the United States south of 
Alaska. At the same time, a great area east of the Cordilleran 
mountain system, some 4,000,000 square miles in extent (Fig. 170), 



THE GLACIAL PERIOD 253 

and lying partly in Canada and partly in the United States, was 
covered with an ice-sheet. 

The ice-sheet of North America originated in two principal cen- 
ters, one on either side of Hudson Bay. The beginning of each was 
doubtless a great snow-field. At first these snow- and ice-fields grew 
by the addition of snow, and later also by the spread of the ice to 
which the snow gave rise. The two ice-sheets finally became one 
by growing together. This great continental glacier did not origi- 
nate in mountains, but on high plains. 

When largest, the ice-sheet had the extent shown in Fig. 170, but 
there was an area of 8,000 to 10,000 square miles, mainly in south- 
western Wisconsin, over which the ice did not spread. This is known 
as the driftless area, because there are no ice deposits (drift) in it. 
In the Cordilleran mountains there was also a great body of ice 
that remained somewhat distinct from the one which spread from 
the other centers. 

There was extensive glaciation in Europe at about the same time. 
The glaciers of the Alps were then many times as large as those of 
to-day. On the south they extended quite beyond the mountain 
valleys, and spread out on the plains of northern Italy, where they 
left their deposits. Similar conditions existed in. the other mountains 
of Europe where glaciers now exist, and in some where they do not. 
There was also a large ice-sheet in northwestern Europe, but its area 
was only about half that of the ice-sheet of North America. The 
principal center from which the ice spread was the mountains of 
Scandinavia. 

Great ice-sheets are not known to have developed in other con- 
tinents during the Glacial Period, but their valley glaciers were 
very large. 

The history of the Glacial Period was not simple. After the growth of the first 
great North American ice-sheet, it shrank to small size, or disappeared altogether. 
Then followed a relatively warm period, when plants and animals lived in the 
region where the ice had been. Another continental ice-sheet then spread over the 
region from which the first had melted, and extended still farther south. As it 
advanced, the second ice-sheet in places buried the soil which had formed on the 
drift left by the ice of the first epoch. Such soils, here and there containing the remains 
of plants which grew in them, are one means by which it is known that there was 
more than one ice-sheet. A third, fourth, and fifth ice-sheet, each somewhat smaller 
than its predecessor, came and then melted. In other words, there were several 
epochs when ice-sheets were extensive, separated by epochs when they were much 
smaller, or when they had disappeared altogether. The ice-sheets of Europe had a 
similar history. 



254 MODIFICATION OF LAND SURFACES 

Cause of glacial epochs. The development of the great ice- 
sheets was due to a change in climate, and especially to a reduc- 
tion of temperature. The cause of the cold is not known, though 
many explanations have been suggested. The explanation which 
seems most acceptable is that the change of climate was due to a 




Fig. 171. Glaciated surface of limestone. The view shows also the relation 
of drift to the bed-rock beneath. Kelleys Island, Ohio. (Stauffer.) 



change in the constitution of the atmosphere. An increase in the 
amounts of carbon dioxide and water vapor would make the climate 
warmer (pp. 31, 178), while any great decrease in these things would 
make the climate much colder. Good reasons have been suggested 
for variations in the amounts of these substances in the air, and 
also for the heavy snowfall in the regions where the ice-sheets 
existed. Heavy snowfall is quite as necessary as low temper- 
ature for extensive glaciation. 



LAND FORMS DUE TO GLACIAL EROSION 255 

CHANGES DUE TO GLACIAL EROSION 

How glaciers erode. Clean ice, moving over smooth, solid 
rock, would erode little, but ice carrying pieces of rock in its bottom 
wears the surface, even when the latter is smooth and solid. Like 
wind and water, therefore, ice erodes by means of the rock tools which 
it carries. Each kind of tool does its appropriate work. Fine, 
earthy material in the bottom of the ice polishes the rock below, while 
sand and small pebbles make scratches (stria) upon it. Grooves are 
made by bowlders held in the bottom of the ice and forced along under 




Fig. 172. Glacial trough in San Juan Mountains, Colorado. 

great pressure. Meanwhile the tools are themselves polished, 
scratched, and worn smaller. The finest products of the grinding 
have been called rock flour. Polished and striated bed-rock surfaces 
(Fig. 171) are among the clearest marks of the former existence of 
glaciers in many places now free from ice. 

Changes in valleys. Mountain valleys through which glaciers 
pass are widened and deepened, and their walls made smoother 
(Figs. 172 and 173). In many cases the heads of glaciated valleys are 
big, blunt, and steep-sided. Most of the lakes which add so much to 
mountain scenery are (1) in rock basins gouged out of valley floors 
by glaciers (Fig. 173), or (2) behind dams formed by the deposits 
of the ice (Fig. 186). Tributary valleys commonly join their main 
valleys at the level of the latter, but the bottoms of many valleys 
that were deepened and widened by former glaciers are much (in 
some cases 500 to 1 ,000 feet) lower than the lower ends of their tribu- 
taries. In such cases streams descend in rapids or falls from the 
tributary hanging valleys (Fig. 174). Much water power is afforded 



256 



MODIFICATION OF LAND SURFACES 



by such rapids and falls in the mountains of western United States, 
Switzerland, and northwestern Europe. 

The ancient ice-sheet overrode hills and divides as well as valleys. 
In many cases the ice deepened the valleys more than it lowered 
the hills, and where this was true it increased the relief, even though 
it reduced the roughness of the surface. 

Elevations reduced and changed in shape. Hills overridden 
by ice-sheets are worn down and smoothed off, and the wear is 




Fig. 173. A valley in the Needle Mountains, Colorado, cleared of all earth 
and loose rock by a glacier which once passed through it. The moving ice also 
smoothed all the projecting points of rock. 



greatest on the side of the hill against which the ice moves (Fig. 
175). Many small elevations were worn away entirely by the con- 
tinental glaciers. 

Ice-shaped coasts. Glaciers which descend into the sea through 
bays tend to gouge out the bay-bottoms, and to wear back the bay- 
heads. If such glaciers melt away, the sea enters to form long, 
narrow, steep-walled re-entrants, called fiords. Norway (Fig. 176), 
Scotland, Maine, and Alaska have fiord coasts, though all of them 
owe their characteristics in part to sinking. Many islands front 



CHARACTERISTICS OF GLACIAL DEPOSITS 257 



these coasts, most of them representing the higher parts of the old 
land whose surroundings have been drowned. 

GLACIAL DEPOSITS 

General characteristics. Most of the material transported by 
a glacier is carried in its lower part; but some is carried in the ice 
above its bottom, and some on top of the ice. All of it is left, finally, 




Fig. 174. Hanging valley; Nunatak Fiord, Alaska. (Tarr, U. S. Geol. Surv.) 

on the surface of the land. The materials deposited by glaciers, called 
glacial drift or till, range from finest earth to huge bowlders (Fig. 177). 
They are not stratified, 
and in many places are 
so deposited as to form 
distinctive topographic 
features. Much of the 
drift deposited by the 
continental glaciers is 
a thorough mixture of 
many kinds of mate- 
rial, for it was derived 
from a vast area within 
which many kinds of 
rocks occur. (Com- 
pare glacial drift with 
stream deposits.) 

Leading types. When the end of a valley glacier or the edge of 
an ice-cap stays in the same place for a long time, a thick body of 




Fig. 175. A hill smoothed by the glacier ice 
which overrode it. Shore of North Greenland. 
(From photograph by Chamberlin.) 



258 



MODIFICATION OF LAND SURFACES 



drift is lodged beneath it, for drift is brought to this position all the 
time by the oncoming ice, and left there. Such a deposit is a terminal 
moraine (Fig. 178). All the other drift deposited by an ice-sheet is 
ground moraine. After a glacier melts, the area of ground moraine is 




Fig. 176. The Sogne Fiord, coast of Norway. (Robin.) 



not as great as the glaciated area, for glaciers do not carry debris in all 
parts of their bottoms. In general, the drift is thickest and covers 
the largest proportion of the surface near the margins of a glaciated 
area, and is thinnest and least continuous in the region from which 

the ice spread (Why?). 
For this reason, there 
are large areas of bare 
rock and of thin, bowl- 
der-strewn soil on the 
uplands of eastern and 
northeastern Canada. 
Together with a bleak 
climate, these condi- 
tions render large areas 
unfit for farming. 
Much of the material 
removed by the ice 
from Canada was de- 
posited in the United 
States. The lateral 
moraines are left along the sides of a valley after the valley glacier 
is melted (Fig. 179). Some of them are hundreds of feet high. 

Surface features. Because glaciers distribute their drift very 
unevenly, large areas once covered by ice are marked by hillocks, 




Fig. 177. Section of unstratified drift near 
Henry, Illinois. (Crane.) 



SURFACE FEATURES DUE TO ICE DEPOSITS 259 

mounds, ^and ridges of drift, and by basin-like or trough-like depres- 
sions. These features are most pronounced in terminal moraines, 
the surfaces of which may be distinctly rough and hummocky (Fig. 180). 




Fig. 178. A glacier in the Cascade Mountains, Washington. Shows spreading 
end of glacier, crevasses in ice, and terminal moraine. (Willis, U. S. Geol. Surv.) 



In the Lake States, the rougher parts of the terminal moraines 
commonly are used for woodlots and pastures (p. 173), for the sur- 
face is too uneven and the soil too coarse and stony to be cultivated 
successfully, in competition with the neighboring prairies. Many 
of the hollows in the surface of the drift contain lakes (p. 261), ponds, 



260 



MODIFICATION OF LAND SURFACES 



and marshes (p. 300). It is estimated that there are \]/ 2 million 
acres of marsh land in Minnesota, nearly as much in Michigan, and 

2^ million in Wiscon- 
sin. The total swamp 
area' for the three 
states is larger than 
the combined area 
of Massachusetts, 
Connecticut, Rhode 
Island, and Delaware. 
Nearly all this swamp 
land is the result of 
glaciation. 

The surface of the 
drift is very unlike 
that developed by the 
erosion of running water, for in the latter the depressions have out- 
lets, and the hills and ridges stand in a definite relation to the valleys. 
The drift left by the continental glacier increased the relief in 
some places (Fig. 181), with unfavorable results; but in most places 



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ffi^TT^fiSJffl 








ill 




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Fig. 179. A lateral moraine left by a former 
glacier in the Bighorn Mountains of Wyoming. 
(From photograph by Blackwelcler.) 




Fig. 180. Terminal moraine topography near Oconomowoc, Wis. (Fenneman.) 



it decreased relief and left the surface less rough than before 
(Fig. 182). This made it easier to cultivate the land and to build 
roads. Most of the surface between the Ohio River and the Great 



FORMATION AND DESTRUCTION OF LAKES 261 



Lakes appears to have been made smoother. But for glaciation, 
much of this region probably would have a maturely eroded sur- 
face, not unlike that 
of the driftless area, 
and a poorer soil than 
it now has. 

Deposits beyond 
the land. Glaciers 
which descend into the 
sea may build subma- 
rine banks and even 
islands. Along the 
eastern coast of North 
America, these deposits 
may have reached the 
edge of the continental 
shelf in some places. 
Martha's Vineyard, 
Nantucket, and Long 
Island are composed 

largely of drift. The sheltered waterway behind Long Island 
favored the early growth of sea interests in southern New England. 




Fig. 182. 

Fig. 181. Diagram showing how a nearly level 
surface may be replaced by a rough one through the 
uneven deposition of drift. 

Fig. 182. Diagram showing how glacial drift 
may replace a hilly surface with a fairly level one. 




Fig. 183. Map showing the abundance of lakes in parts of the glaciated area. 
(From Barrett, Minnesota, Sheet, U. S. Geol. Surv.) 

Glacial lakes. The thousands of lakes in northern United 
States (Fig. 183) and Canada are nearly all of glacial origin. Some 
are in basins gouged out of the bed-rock (Fig. 184); some are in the 



262 



MODIFICATION OF LAND SURFACES 



unfilled portions of drift-choked preglacial valleys; and many are in 
hollows in the surface of the drift (Fig. 185). The terminal moraines 
of many valley glaciers form dams, ponding the waters of the streams 
above, making lakes (Fig. 186). 

The smaller and shallower of these lakes and ponds are being destroyed rapidly 
by (1) the sediment washed into them from the tributary slopes, and (2) vegetable 
matter. Some are being drained slowly (Why slowly?) by the erosion of their 
outlets. In the future, many of the shallower ones will be drained by man, that 
he may use their bottoms as farm land. It has been estimated that there are 
8,000 lakes, big and little, in Minnesota, and that half of them will be destroyed 

by natural processes within fifty years. 
Connecticut has been credited with hav- 
ing had some 4,000 lakes at the close of 
the Glacial Period; 2,500 of them have 
been destroyed, and the sites of many 
of them now form choice garden spots. 
In southern Michigan and Wisconsin 
many early settlers located their farms 
on the bottoms of former lakes, attracted 
by the flat land and the fine, easily- 
worked soil. 

Deposits of marl occur in and about 
some glacial lakes. This marl is a soft, 
limey earth, the calcium carbonate of 
which is contributed chiefly by the shells 
of fresh-water mollusks and by lime- 
secreting lake plants. In parts of Mich- 
igan and northern Indiana, these deposits 
are used in making Portland cement. 




Fig. 184. Section of a lake in an 
ice-scoured rock basin. 




Fig. 185. Section of a lake lying 
in a hollow in the surface of the drift. 




Fig. 186. Section of a lake behind 
a barrier of drift. 



The lakes and swamps of the 
glaciated region make the streams 
flow more steadily through the 
year by holding back some of the water of wet times, letting it flow 
out in times of drought. The drift itself exerts a similar influence, 
for, on the whole, it is thicker than the mantle rock of other regions, 
and therefore absorbs more water, which it yields up slowly, making 
the supply of ground-water to streams more steady than it would 
be otherwise. Thus floods are less numerous and less dangerous, and 
the value of the streams for navigation and power is increased. 
By reducing or preventing floods, the porous drift and the lakes also 
greatly reduce soil erosion. 

Certain lakes which came into existence along the margin of 
the continental glacier disappeared with the ice. One of the largest 
of the marginal lakes (Lake Agassiz) lay in the valley of the Red 



LAKE AGASSIZ 



263 



River of the North (Fig. 187). This lake covered an area greater 
than that of all the Great Lakes. The water, however, was shallow. 
It came into existence when the edge of the retreating ice lay north of 
the lake, and blocked drainage in that direction. The water rose in 
the basin until it overflowed to the south, finally reaching the Missis- 
sippi River. When the ice at the north melted back far enough, a 










ksj 



SUPERIOR £ %£ 



Fig. 187. Map of extinct Lake Agassiz, and other glacial lakes. Lake Winni- 
peg occupies a part of the basin of Lake Agassiz. (U. S. Geol. Surv.) 



new and lower outlet was opened to Hudson Bay, and the lake was 
drained. Lake Winnipeg and several smaller lakes may be regarded 
as remnants of Lake Agassiz, for they occupy the deepest parts of the 
old basin. 

As late as 1870 the floor of extinct Lake Agassiz was almost 
unoccupied by farmers (Fig. 188), but during the next few years 
its soil was found to produce a fine grade of hard wheat, and a great 
tide of farm-seekers turned to the region (Fig. 189). On the nearly 
level lake floor it was possible to plow league-long furrows in straight 
lines, and later to do much of the work by such labor saving machines 



264 



MODIFICATION OF LAND SURFACES 



as the steam plow. Ft. Gary quickly grew into the city of Winnipeg, 
and the wheat of the region helped to make Minneapolis the leading 
flour manufacturing city of the United States (p. 288). 

The Great Lakes did not exist, so far as known, before the Glacial 
Period, but river valleys probably extended along their longer diam- 
eters. Lake basins were made as a result of (1) the deepening of these 
valleys by ice erosion, (2) the building up of the rims of the basins 



• I \\}nier2prrvyrr.:, 

E~!6*ol8 • • • 




Fig. 188. Fig. 189. 

Fig. .188. Map showing distribution of population in region of Red River of 
the North in 1870. 

Fig. 189. Population map of region of Red River of the North in 1880. 



by the deposition of drift, and perhaps (3) the down-warping of the 
sites of the basins. The influence of the Great Lakes on climate and 
on certain industries has been noted in earlier connections. Their 
importance as commercial highways is considered in Chapter XVI. 

Hundreds of the glacial lakes are of great benefit to man as pleasure and 
health resorts, and as sources of water supply. Many have become famous through 
their fine summer residences, and very many more are visited by numerous camping, 
boating, and fishing parties. In these ways the lakes have become large factors for 
good in the life of the people. 

Effect of ice deposits on stream courses. The deposition of 
drift rilled many of the former valleys. After the ice melted, the 
surface drainage followed the lowest lines open to it; but these lines 
did not always correspond with the former valleys, for some of the 
latter had been filled, and most of them were blocked up in some places. 



BENEFITS RESULTING FROM GLACIATION 265 



The surface waters therefore followed former valleys in some cases, 
and in others flowed where there had been no valleys. In choosing 
their new courses, the streams in places ran down steep slopes or 
fell over cliffs. Many of the rapids and falls of the glaciated area, 
so important in the economic life of the country (p. 288), came into 
existence in this way. 

Glacial soils. In the United States, glaciation increased the 
amount of mantle rock, and improved the quality of the soil in 
many places. Much of the latter is good because it is a thorough 
mixture of material derived from many kinds of rock, and so is well 
supplied with all the mineral elements necessary for plants (p. 169). 
It is instructive to compare Fig. 257, showing the relation of the im- 
proved acreage to the total farm acreage in the different states, with 
the map showing the glaciated area (Fig. 170). Iowa, Illinois, Indi- 
ana, and Ohio are seen to lead 
in the relative amount of their 
improved land. Glaciation is 
perhaps the most important 
fact in the geography of each 
of these states, and it has 
greatly furthered their high 
rank in agriculture. 

The benefits which the states 
between the Ohio River and the 
Great Lakes received from glaciation 
may be illustrated further. Fig. 190 
shows the glaciated and unglaciated 
parts of Ohio. The unglaciated part 
belongs to the Alleghany Plateau. 
It is in a mature stage of erosion, and 
the thin, sandy soils on the steep 
slopes wash easily. The first settle- 
ment in Ohio was made in this part 
of the state, at Marietta; but soon 

the tide of settlement set toward the more attractive glacial plains farther west and 
north, and the population of most of the unglaciated counties remained relatively 
sparse until the mineral resources of the region were developed. Many farmers in 
the unglaciated section turned their attention to sheep-raising when they found 
they could not grow grain for export in competition with the farms of the glaciated 
area, and grazing was long an important industry in the southeastern part of 
the state. 

About four-fifths of Indiana were glaciated. On the average, the glaciated 
land is worth about twice as much as the unglaciated, and the yields of staple 



j— — y,, 

i 
i 

1 i 
i 

i 


^f*^ 


\ 

fl V 

\\ 

f i 
f i 
i 



Fig. 190. Map showing the glaciated 
(shaded) and unglaciated portions of Ohio. 



266 MODIFICATION OF LAND SURFACES 

crops bear a similar relation. The southern boundary of the region within which 
4,500 bushels of corn are grown per square mile is the margin of the latest drift 
sheet. The situation is much the same in Illinois. 

The quality of the soil in places was injured by glaciation. In 
some of these places the drift is very thin, while in others it is very stony, 
so that great labor is necessary to put it in workable condition. 
Again, the drift may be too sandy or gravelly to make good soil, or 
its surface may be too rough (pp. 173, 259). 

Special uses of glacial deposits. Much drift clay (rock flour) is used for mak- 
ing brick, tile, and other clay products. Ohio has been the leading state in the clay 
industry for many years, because of the abundance of raw clay, part of which is 
drift, cheap near-by fuel, excellent shipping facilities, and nearness to great markets. 
About 1 ,000,000,000 bricks are made from glacial clay each year in the vicinity of 
Chicago. The gravel of the drift is used extensively for road making, and in the 
manufacture of various kinds of cements. 

DEPOSITS BY GLACIAL WATERS 

Water flows in abundance from all glaciers in the summer, and 
from many glaciers all the time. Stream work, therefore, accom- 
panies glaciation in all cases, and much of the drift left by ice is 
modified by water afterward. 

Streams which flow from glaciers carry so much sediment that 
in many cases they build gravelly or sandy plains beyond the ice. 
Such a deposit in a valley below a glacier is a valley train. Valley 
trains are developed best just outside terminal moraines. The 
Rock River, in southern Wisconsin, filled its valley with gravel and 
sand to a depth of 300 to 400 feet just outside the terminal moraine 
of the last glacial epoch. The Columbia River filled its valley 
to the depth of 700 feet in places with sediment washed out from the 
ice. Since the ice-sheet melted, parts of most of the valley trains have 
been carried away, and their remnants are terraces (Fig. 162). Drift 
terraces are common features of many of the valleys of south-flowing 
rivers in the glaciated area and just south of it. 

Streams which issue from an ice-sheet and fail to find valleys 
build alluvial fans. By growth, these' fans may unite, making an 
outwash plain, very much like a compound alluvial fan. Like valley 
trains, outwash plains are developed best just outside the terminal 
moraines of ice-sheets, and their materials are stratified. East New 
York, Woodhaven, Jamaica, and other suburbs of Brooklyn grew up 
on the outwash plain of Long Island before the terminal moraine 



DEPOSITS BY GLACIAL WATERS 267 

just to the north was much settled. (What were the probable rea- 
sons for this?) 

Deltas may be built in lakes at the ends or edges of glaciers, 
and the deposits made by waters beneath the ice and at its edge 
take on locally the form of ridges and hillocks. 

As a glacier melts away, the waters produced by the melting 
flow over the surface of the drift which the ice had deposited, and 
modify it more or less by eroding in some places and depositing 
in others. As a result of all these phases of water work, much of 
the drift is stratified. 

Summary. Although less important, ice takes its place with air 
and water as one of the three agents which modify land surfaces. 
From this standpoint, its principal mission is the wearing of the land 
and the moving of the waste toward the sea. Through their wide- 
spread effects on topography, soil, drainage, and the distribution of 
plant and animal life, the ancient ice-sheets are far more important 
than the glaciers of to-day, as factors in human affairs. Existing 
glaciers are valuable to man chiefly in connection with the develop- 
ment of power on the streams which flow from them. 



QUESTIONS 

1. In northern United States and Canada, would floods which occur as the 
river ice breaks up in spring be more likely to be disastrous on north-flowing or 
south-flowing streams? Why? 

2. Why are there more glaciers in the Sierra Nevada and Cascade mountains 
than in the Rocky Mountains? Why are there more in Montana than in Colorado? 

3. State all the factors which influence the size of a valley glacier. 

4. Compare and contrast typical topographies due to (1) glaciation and (2) 
river erosion. 

5. (1) What are all the important ways in which human interests have been 
(a) benefited and (b) injured by the work of the ancient ice-sheets in the United 
States? (2) On the whole, was glaciation beneficial or injurious? 

6. Why are the effects of glaciation more favorable, from the standpoint of 
man, in northern United States than in northeastern Canada? 



CHAPTER XVI 
THE USES AND PROBLEMS OF INLAND WATERS 

Many ways in which streams and lakes affect human interests 
have been noted in preceding pages. In the present chapter, inland 
waters are considered from the standpoints of navigation, power, 
irrigation, drainage, and water supply. 

Navigation 

In the early development of many countries, lack of roads led to 
the use of the waterways for trade and travel. Even after roads 
had been built, transportation by water was much cheaper than 
transportation by land in most cases, and traffic continued to use 
waterways where ^they were available. Where railroads have come 
into competition with waterways, the latter in most cases have lost 
much of their traffic. The waterways of some countries have been 
protected by law against ruinous railroad competition, and certain 
waterways, for example the Great Lakes, furnish such favorable 
conditions for transportation that their traffic has grown in spite 
of the railroads. The average cost of hauling over the railroads in 
the United States declined from j 1 /^ cents a ton per mile in 1837, 
to less than 4/ s of a cent per mile in 1905; yet under favorable con- 
ditions, the cost of transportation by water is estimated to be only 
J / 4 to 1 /t ) that by rail. In 1909, rates for iron ore on the Great Lakes 
were less than one mill a ton per mile, while the rates for ore by rail 
were about one cent a ton for the same distance. 

RIVER NAVIGATION 

Streams were the first waterways to be used regularly for com- 
merce. The Euphrates and Nile were among the rivers to which men 
first entrusted themselves and their goods. After a time, river 
navigation led to coastwise navigation, but to the end of the Mediaeval 
Period there was little or no navigation of the open ocean. It is 
only in the Modern Period that navigation of the open sea has per- 
mitted the development of world-wide commerce. 

268 



THE GREAT RIVERS OF THE WORLD 269 

Leading rivers of foreign lands. Because of its relief (p. 24), 
few of the rivers of Asia are important highways of commerce. The 
Yang-tze is the greatest highway. Fed by the snow-fields of the 
mountains of Tibet, and flowing to the Pacific through some of the 
most densely populated provinces of China, it is both one of the long- 
est rivers in the world, and one of the most important commercially. 
Large ocean steamers go up 600 miles to Hankow; smaller steamers 
ply the river 500 miles farther, to the mouth of the gorges; and 
native junks go up many miles more. The Hwang-ho, the other 
great river of China, flows through a densely settled region, but is 
nearly useless for navigation because of its shifting and silt-choked 
channel. 

In India, the Ganges and Indus present a contrast similar to that 
of the Yang-tze and Hwang-ho. The Ganges traverses the most 
populous and wealthy provinces, and has been of great significance 
throughout the history of India. It is fed by many Himalayan tor- 
rents, and flows for about 1200 miles across the alluvial plains of the 
north. Ocean steamships ascend the Hugh, one of the mouths 
of the Ganges, to Calcutta, and the river is used more or less for 
navigation to the base of the mountains. The Indus River is used 
but little by steamers, because of many sand bars and frequent 
changes in the channel. Together with its larger tributaries, it is 
valuable chiefly for irrigation. The great rivers of Siberia are navi- 
gable for hundreds of miles, but their value is lessened because they 
flow to the Arctic Ocean. 

The relief of Africa limits the navigation of most of its rivers to 
relatively short distances (p. .25). The Nile has regular steamboat 
service to the First Cataract, but navigation is not easy in the delta 
portion of the river below Cairo. Above the cataracts, the river is 
navigable throughout the year for long distances. 

Throughout the history of Russia its rivers have been its chief 
highways. Even to-day, they have greater relative importance 
than the rivers of western Europe, because other means of trans- 
portation are less satisfactory; wagon roads are poor and railroads 
few. Most of the Russian rivers rise in the vicinity of the Valdai 
Hills and follow long courses across low, nearly level plains. Their 
currents, therefore, ordinarily are gentle. They are navigable through- 
out most of their courses, and the different systems have been joined 
by canals, so that there is water connection between the Caspian, 
Black, Baltic, and White seas. While the above conditions are 



270 USES AND PROBLEMS OF INLAND WATERS 

favorable to commerce, navigation of the Russian rivers is attended 
by serious drawbacks. They are ice-locked in winter (p. 246), 
subject to great floods in spring, affected by sand bars which hinder 
navigation at low stages, and most of them are tributary to inland 
seas. The Volga is the most important Russian river, and the 
largest river of Europe. Together with its tributaries, it is said to 
afford 7,500 miles of navigation. Its usefulness is lessened by the fact 
that its lower course is through a semi-arid region, and by the fact 
that it ends in a land-locked sea. 

Most of the larger rivers of central and western Europe are 
important commercially, and large sums have been spent to improve 
them and extend their connections by canals. In Germany, river 
transportation increased more than fivefold in the thirty years 
preceding 1905, although Germany has a greater railroad mileage than 
any other country in Europe. This is in striking contrast with the 
situation in the United States (p. 278). The rivers and canals of 
Germany (p. 287) furnish from 8,000 to 10,000 miles of navigable 
waterways. So much work has been done in dredging, straightening, 
and otherwise improving the larger rivers, that it is said scarcely one 
of them flows in a natural channel. 

The Rhine has influenced the history of Germany more than any 
other river, and is to-day the most important commercial river in 
Europe. Fed by melting snows in Switzerland and made steady in 
its flow by passing through Lake Constance, it flows through western 
Germany and the Netherlands, into the North Sea. Rotterdam, 
on the Rhine delta, is one of the greatest ports of continental Europe, 
and Cologne, though far inland, is practically a seaport. The fertile 
valley of the Rhine is settled densely. Commercially, the Elbe is 
the second river of Germany, though much less important than the 
Rhine. The traffic on these rivers is largely in heavy freight, such as 
coal and grain. 

The Danube has been an important highway since early times. 
Like many other delta-building rivers, it was difficult to enter until 
jetties were built at its mouth. Extensive improvements have been 
made also at the "Iron Gate," and elsewhere. The Rhone is the 
largest river of France, and its valley is the natural highway into the 
country from the south. Navigation in the delta portion of the stream 
was hindered by shallow and shifting channels, and large sums have 
been spent in improvements. Even now, however, the Rhone is not 
navigable for large ships. The Po and the Ebro are the only other 



THE GREAT RIVERS OF THE WORLD 



271 



European streams of importance flowing into the Mediterranean, 
and neither is used much for navigation. 

In Great Britain, the rivers are comparatively short, but their 
value is increased by the fact that their lower courses are drowned, 
and subject to rather high tides. The tides help to make Liverpool 
and London great seaports, though both are on small rivers. Like 
the United States, Great Britain has neglected, till recently, the 
question of waterway improvement. To-day transportation in Eng- 
land is said to be the most expensive in Europe. 




Fig. 191. Map showing principal streams in the United States actually used 
for purposes of transportation (1906). Only the parts so used appear on the map. 
(Data from map by U. S. Bureau of Corporations.) 

The Amazon is the largest river in the world, with a length of 
about 4,000 miles. Ocean steamers can go up 1,000 miles, and with 
its 29 large tributaries it furnishes more than 20,000 miles of navigable 
water, most of it through dense forests. The river is used to carry 
out tropical woods, rubber, and other products. The Orinoco is 
navigable for small boats to within 100 miles of Bogota, and the La 
Plata System is navigated by steamers for long distances. 

Besides the great rivers mentioned above, there are many others 
which serve as highways of trade and travel. 

Navigable streams of the United States. There are about 300 
streams in the United States that are navigated more or less (Fig. 



272 USES AND PROBLEMS OF INLAND WATERS 

191). Their total navigable length is about 26,400 miles — more 
than the circumference of the earth. Only a few have much com- 
mercial importance now, and many are used only by small boats 
engaged in local trade. As Fig. 191 shows, most of the navigable 
streams are in the eastern half of the country. The absence of 
navigable waterways (Why absent?) has been a serious disadvantage 
to much of the West. 

The principal rivers, and the part which they have played in 
the development and commerce of the country, are discussed briefly 
in the following paragraphs. Most attention is given to the Mis- 
sissippi System, because it is by far the most important. 

Atlantic Rivers of United States 
On the Atlantic slope there are nearly 150 streams navigable 
for varying distances from the sea — in most cases only to the head 
of tide-water. The rivers of New England are navigable for short 
distances only, because of falls and rapids. 

The Connecticut is navigable to Hartford; the Merrimac to Haverhill; the 
Saco to Saco and Biddeford; the Kennebec to Augusta; and the Penobscot to 
Bangor. All these cities receive much freight by water. Many streams of central 
and northern New England are used for rafting lumber and floating logs. 

Although the streams of New England afford little navigation, the larger val- 
leys have been important highways since the settlement of the region began. They 
guided fur traders, lumbermen, and farmers (p. 219) into the interior. They 
•served as lines of advance and retreat for Indian war parties and colonial armies. 
General Arnold invaded Canada in 1775 by way of the Kennebec and Chaudiere 
valleys. To-day many of the valleys are followed by railroads. Boston was 
handicapped greatly in its commercial development by the fact that no large, 
navigable river came to it from the interior. 

The Hudson is the most important, commercially, of the tribu- 
taries to the Atlantic from the United States. Because the Hudson 
Valley is drowned, deep water extends 100 miles inland, and the river 
is navigable 50 miles farther, to Troy. 

The belt of relatively weak rocks along which the Hudson Valley developed 
contains, farther north, Lake Champlain and the Richelieu River. This long, 
narrow lowland, which extends from New York City to the St. Lawrence River 
near Montreal, was called by the Indians "The Grand Passway." General 
Burgoyne (1777) and General Prevost (1814) used it to invade the United States. 
When the Champlain Canal was opened between the Hudson River and Lake 
Champlain. water transportation was possible throughout its entire length. The 
Mohawk Valley and the low plain to which it leads furnish an easy route between 
the Hudson River and Lake Erie; the highest point is only 445 feet above sea-level. 



RIVERS AS FACTORS IN COLONIAL LIFE 273 



Its drowned-valley harbor and good connection with the interior have been leading 
factors in the growth of New York City. 

South of the Hudson River, most of the larger rivers are navigable 
to the "fall line," where the streams, in passing from the hard rocks 
of the Piedmont Plateau to the weak rocks of the Coastal Plain, have 
developed falls and rapids. Along this line are Philadelphia, Balti- 
more, Richmond, Petersburg, 




Raleigh, Columbia, Augusta, 
Macon, and Columbus (Fig. 192). 
Ocean-going vessels ascend the 
Delaware River to Philadelphia, 
and smaller boats go up to 
Trenton. Several drowned trib- 
utaries of Chesapeake Bay, 
itself a drowned valley, have 
some commercial importance. 

The drowned streams of the Vir- 
ginia region were deep enough for 
the light-draft boats of the colonial 
period, and served the settlers as 
roadways. The early plantations were 
arranged in narrow belts along the 
stream courses. For a century, travel 
in tidewater Virginia was largely by 
water; little attention was given to 
road building. Ships came from Eng- 
land direct to the wharves of many 
of the plantations, to exchange for 
tobacco the manufactured goods 
needed in the colony. Under these 
circumstances, no important collect- 
ing and distributing centers devel- 
oped. To 1700, Jamestown was the only place worthy of being called a village. 
In South Carolina, the streams were not drowned sufficiently to render many of the 
smaller ones navigable. Hence Charleston became the commercial center of the 
colony, and soon also the social and political center. In general, freight rates de- 
crease as the size of the cargo increases, and accordingly the tendency has been to 
build larger and larger boats. As a result, many of the streams of the Coastal 
Plain, once important in trade, were long since abandoned by commerce. 

Mississippi River System 
The Mississippi River has more than 50 tributaries that were 
navigated more or less in 1907. The navigable waters of the system 
aggregate nearly 14,000 miles and border or traverse 21 states. 



Fig. 192. Map showing leading cities 
along the "fall line." 



274 USES AND PROBLEMS OF INLAND WATERS 



The Mississippi River itself is navigable for large steamers to St. 
Louis, and for smaller boats to St. Paul. The Ohio River, now much 
the most important, commercially, in the United States, is navigable 
throughout its length. The Missouri River is navigable for small 
boats to Ft. Benton, in Montana, though it is now used but little. 
Other tributaries of the Mississippi are navigable for varying distances, 
as shown by Fig. 191. 

Influence on early development of the West. At the close 
of the Revolutionary War, the Mississippi River was made the 
western boundary of the United States, and the supposed length of 
the river fixed the width (north and south) of the country at that 
time. It was an unsatisfactory international boundary line, for (1) 
its position shifts (p. 240), (2) the navigation of the river by the 
Americans from the east side and any foreign people from the west 
side would have led to friction, and (3) the river basin is a natural 
unit. The political unity of the Mississippi Basin was brought 
about by the Louisiana Purchase in 1803. 




Fig. 193. A typical flatboat. 

The early western settlers could send over the difficult mountain 
roads to the eastern seaports only valuable articles of little bulk and 
weight, such as whiskey, furs, and ginseng, or live stock, which could 
walk to market. For years, many thousands of hogs and cattle 
were driven over the mountains to Charleston, Baltimore, and 
Philadelphia, but salted and dried meats, flour, tobacco, and the other 
export products of the frontier had to go down the Mississippi River 
to New Orleans. Roads were few and poor, and the settler found 
it highly desirable to locate his farm within easy hauling distance 
of a navigable stream. The influence of navigable waterways upon 
the distribution of population is shown clearly by the census maps 
of 1820 (Fig. 278) and several later years. 



THE STEAMBOAT AND WESTERN DEVELOPMENT 275 



One of the most used of the early boats on the western rivers 
was the flatboat, commonly 1 5 feet wide and 40 to 50 feet long (Fig. 
193). While these boats served for downstream navigation, they 
were almost useless against the current of the Mississippi. Ordinarily 
they were broken up and the lumber sold at New Orleans. In these 
early days, freight was carried up-river largely in keel boats or barges. 
Most of them were equipped with oars, poles, and sails, and in many 
cases they were dragged upstream by men on the bank, tugging at a 
long rope. The average length of the trip from New Orleans to 
Louisville was three months, and in many cases it required four 
months. 

Influence of steam navigation on the development of the 
Interior. The first steamboat appeared on the Ohio River in 181 1, 
and within a few years it was seen that steamers could cope success- 
fully with the currents of the rivers of the Interior, and that they 
would increase greatly the commercial value of the streams (Fig. 194). 




Mississippi River steamboats at New Orleans. 



For a time, they could not be built fast enough to take care of the 
business. By 1850, the time involved in upstream travel had been 
reduced to about Vi8 of what it had been before the appearance of 
the steamboat. This meant, for example, that the steamboat 
brought New Orleans nearly as close to St. Paul, for certain purposes, 
as it had formerly been to Baton Rouge. In 1830 the cost of travel- 
ing by water from New Orleans to Pittsburgh was about % what it 



276 USES AND PROBLEMS OF INLAND WATERS 

had been before the* days of the steamboat. In general, the steam- 
boat soon reduced freight charges to about K of what they had been, 
and finally to % and less. Because of these things, steamboat navi- 
gation became one of the greatest factors in the development of the 
Interior. 

The population of the Interior, commercially dependent for the 
most part on the rivers, increased from 2>^ millions in. 1820 to 6>i 
millions in 1840. Probably no single factor contributed more than the 
steamboat to the rapid expansion of population during these years. 
Thousands settled along the tributaries of the Mississippi having 
steamboat service, and almost over-night river towns sprang up at 
favored points. The total value of the commerce of the western 
rivers in 1850 was estimated at $550,000,000. 

The leading centers of steamboat trade. During the period 
of steamboat supremacy, the river commerce of the Interior centered 
largely in four cities — Pittsburgh, Cincinnati, St. Louis, and New 
Oder ns. 

For some time before the opening of the Erie Canal (1825, p. 286), 
Pittsburgh was the eastern gateway to the Mississippi Basin. Im- 
portant roads connected it with the eastern seaboard. Its position 
at the junction of the Monongahela and Allegheny rivers gave it many 
advantages. The former brought coal from West Virginia, while the 
latter gave it command of the white pine of western New York. The 
principal products of the Pittsburgh mills reflected these advantages, 
together with the command of iron and the products of the surround- 
ing farms. They were implements and machinery, iron ware, cabinet 
ware, lumber, furniture, flour, and liquors. These things were sent 
by river throughout the Interior. 

Cincinnati had several marked advantages for the develop- 
ment of river trade. Situated midway on the Ohio and near the 
northernmost point of the great bend of the river, it was the nearest 
important river town for a large and fertile region north of the Ohio. 
It was also opposite the Licking Valley in Kentucky. The deep 
channel and favorable bank of the river along the city front made 
it easy to handle steamboat traffic. It was connected (in 1832) by 
canal with Lake Erie (Fig. 200). It received by river most of the 
implements and supplies, or the materials for their manufacture, 
needed by the tributary farming region. By river the city shipped the 
products of her flour mills, breweries, distilleries, and slaughtering 
and packing houses, which had been established to use the products 






LEADING CENTERS OF STEAMBOAT TRADE 277 

of the surrounding country. (Why was it desirable to manufacture 
these things near the points where the grain and animals were pro- 
duced?) These advantages made Cincinnati the leading city of 
the Ohio Valley. 

For years most of the capital and business enterprise of St. Louis 
were engaged in the river trade, though later the city became an 
important manufacturing point. The following were the chief advan- 
tages which made it, next to New Orleans, the greatest steamboat 
center on the Mississippi System. (1) It is situated near the mouths 
of the Missouri, Illinois, and Ohio rivers. (2) The Mississippi River 
is considerably deeper below St. Louis than above. At St. Louis, 
therefore, cargoes were exchanged between the lighter-draft boats 
of the river above and those of heavier draft plying on the' river 
below. 

Because of its commanding position near the mouth of the Mis- 
sissippi River, New Orleans had for years the greatest commerce 
of any city west of the Appalachian Mountains. The population of 
New Orleans more than doubled between 1830 and 1840, in spite 
of the growing sand bars at the mouths of the river, frequent inun- 
dations, and disease (p. 243). No other important American city 
grew so fast. But even before the Civil War, the commerce and 
growth of New Orleans had received several serious blows. When 
canals were opened between the Great Lakes and the Ohio, Wabash, 
and Illinois rivers (p. 286), enormous quantities of goods from Ohio, 
Indiana, Illinois, and even from parts of Iowa and Missouri, went to 
the eastern markets by way of the Great Lakes and the Erie Canal, 
rather than to the southern markets. New Orleans particularly was 
injured as an importing city. It is some 1500 miles farther than New 
York from the cities of northwestern Europe, and the connection of 
New York with the Interior by way of the Hudson River, Erie Canal, 
and Great Lakes, was easier than that of New Orleans against the 
current of the Mississippi. The railroads continued the work of the 
canals, and made trade along east- west lines vastly greater than that 
along north-south lines. 

In addition to the four cities mentioned, many smaller cities 
and villages depended largely on river trade. Such were Louisville, 
whose location was determined by the rapids of the Ohio River; 
Nashville and Kansas City, profiting commercially (Why?) from their 
respective positions on the great bends of the Cumberland and 
Missouri rivers; and Peoria, the leading city of the Illinois Valley. 



2 78 USES AND PROBLEMS OF INLAND WATERS 

Decline of river navigation. For years, commerce on the 
Mississippi River and its tributaries has been relatively small. The 
decline began at different times on different rivers — for example, 
in 1855 on the Illinois River, and about 1883 on the Yazoo River. The 
causes of the decline also differed somewhat, but the leading ones were 
of general application. (1) The channels of many of the rivers were 
shallow, crooked, and shifting. (2) The depth of water varied much 
from time to time, and from place to place. Boats suited best to the 
Great Lakes or coastwise trade could not be used on rivers or canals 
having but 6 feet of water, and boats giving the cheapest service for 
6 foot channels could not be used in shallower waters, and so on. 
This was especially serious because of the importance of through 
traffic in American transportation. The great size of the United 
States and the contrasted products of its different parts mean that- 
much freight must move long distances. (3) The use of the rivers 
forced freight in many cases to take roundabout courses. (4) The 
waterways in the central and northern parts of the country were 
closed by ice a part of each year (p. 246). (5) Water transportation 
was relatively slow. (6) In general, the methods, landing places, 
etc., of river and canal trade have remained unimproved since the 
Civil War, and have been less and less able to meet the demands of mod- 
ern business. (7) When railroads were built throughout the Interior, 
these disadvantages proved fatal to river trade. The railroads at 
once got most of the passenger trade, and most of the traffic in perish- 
able and expensive freight. The rivers could, and in the future can, 
hope to compete only in the transportation of heavy, bulky, and 
non-perishable commodities such as coal, grain, lumber, building 
stone, and the like. It is highly desirable that the navigation of 
the larger rivers be improved, so that they may help the railroads 
in transporting the ever-increasing quantities of cheap freight (p. 287). 

Even since the loss of most of their business, many of the water- 
ways have been of importance in regulating railroad freight rates. 
Most of the river towns that obtained good railroad connections 
did not suffer greatly from the decline of river trade; but to river 
towns without railroads the passing of the steamboat was a serious 
blow, and many such places decreased in population. 

Present traffic. The Ohio and its tributaries now have the 
largest river trade in the country, and Pittsburgh is the leading inland 
city in the volume of its river commerce. The traffic is mainly in 
coal, lumber, logs, sand, and gravel. On the upper Mississippi, the 






FEATURES OF THE GREAT LAKES 279 

declining traffic is largely in rafted logs and lumber, and in sand. 
The principal things transported on the lower Mississippi are coal, 
lumber, crude petroleum (from Louisiana), and plantation products 
such as cotton, sugar, and rice. 

In 1906, the total traffic for the entire Mississippi System, includ- 
ing rafts and harbor traffic, amounted to only about 30,000,000 
tons. As in early days, most of the freight moves downstream. 

Pacific Rivers of the United States 
The rivers of the United States tributary to the Pacific Ocean 
have a combined navigable length of about 1,600 miles. None of 
them affords navigation far inland (Fig. 191), the San Joaquin and 
Sacramento rivers, especially, being nearly parallel with the coast. 
The Columbia is commercially the most important river of the Pacific 
coast. Ocean steamships reach Portland (some miles up the Willa- 
mette), no miles inland. 

As the only river rising east of the Cascade-Sierra Nevada ranges and directly- 
tributary to the Pacific Ocean, the Columbia was the key to political expansion 
on this portion of the coast. The fact that its branches approach closely the 
headwaters of the Saskatchewan and Missouri rivers, along which English and 
American explorers and fur traders advanced, was sufficient to cause a dispute 
between Great Britain and the United States over the Oregon country. 

The Colorado River is navigable for light-draft boats in its lower 
course (Fig. 191), but is little used commercially. 

COMMERCE OF THE GREAT LAKES 

General features of the lakes. The Great Lakes are the most 
important inland waterways in the world. Their shore-line in the 
United States is more than 4,300 miles long, if all the minor irregu- 
larities are measured. They are connected by canals with the At- 
lantic Ocean and the Mississippi System (Fig. 200). Unfortunately, 
the shores of the Great Lakes have few naturally good harbors. 
Several of the leading cities and many of the villages on them had their 
locations determined chiefly by the mouths of creeks or rivers. Thus 
Buffalo was located in part by the mouth of Buffalo Creek, Cleve- 
land by the mouth of the Cuyahoga River, and Chicago by the river 
of the same name. The entrances to these and similar streams 
were shallow, and easily choked by drifting sands. As a result, 
harbor improvements have been needed frequently throughout the 
history of the cities concerned. 



280 USES AND PROBLEMS OF INLAND WATERS 

The Great Lakes afford conditions for transportation in many- 
ways vastly superior to those of the rivers, and their commerce 
has grown rapidly. The principal commodities carried on the Lakes 
are iron ore, coal, lumber, and grain — raw materials of great bulk, 
and not requiring rapid transportation. In 1910, the total domestic 
shipments on the Great Lakes amounted to more than 86,000,000 net 
tons, of which more than half was iron ore. 

Early navigation. Apart from their use by the Indians, the 
Great Lakes were navigated first by the French from eastern Canada. 
Their fur traders navigated the Great Lakes in light canoes which 
could be used also on the streams leading to and from the Lakes, 
and could be carried over the many portages. 




^PortageS 



Fig. 195. Portages between the Great Lakes and the Mississippi System. 



Most of the lines which the French used in passing back and forth through the 
Great Lakes region (Fig. 195) are still of importance in trade and travel. Canals 
were cut across several of the old portages (compare Figs. 195 and 200), and turn- 
pikes and railroads followed the old lines or ran parallel to them. A number of 
villages and cities grew up at strategic points where the French had built forts to 
guard the lines of trade. Between Presque Isle (opposite the city of Erie, Fig. 251) 
and the Allegheny River, there ran at different times buffalo trail, Indian path, trad- 
er's trace, military road, turnpike, and railroad. A canal, soon abandoned, also 
once connected the city of Erie with the Ohio River. Long the favorite route of 
the French between the St. Lawrence River and the Great Lakes, the Ottawa 
Valley was followed by the Canadian Pacific Railroad westward from Montreal, 
and is to be followed by the projected Georgian Bay Ship Canal. In connection 



STEAM NAVIGATION ON GREAT LAKES 



281 



with the latter much water power will be made available, and the Ottawa Valley 
probably will become one of the most important industrial sections of Canada. The 
above facts illustrate the truth of a statement that "trade and civilization in 
America have followed the arteries made by geology." 

The first American sailing vessel appeared on the Great Lakes 
in 1797, but for a time the number increased slowly. In 1812 some 
half-dozen small schooners car- 





1 1„ . s^f? 1830 > 

; |UnderZpersq.niL <f V J~ r ~^~T Z. 




E2-6 ...^ /^J3£- 

O6-18 . - - s /^ ryL 


~^S5t~ 


| Q18-45 - • JJ M> \ 




^^45 and over U r J j 
,W\' t *' / \ MICHIGAN^ 




/ ILLINOIS/" |\-— / LJ "JlT X" 1 
\ 1 1 ' /" 1NDIANA ^. 1 \ \ (( 


^~r^> 


vM%W^^k 


^jji0^\ 





Fig. 196. 



ried nearly all the traffic on Lake 
Erie, and for several years more 
the business of the upper lakes 
was limited to that of the fur- 
trading stations. Further devel- 
opment awaited the introduc- 
tion of steam navigation, and 
the settlement of the neighbor- 
ing lake and prairie plains. 

Steam navigation and the 
settlement of the Great Lakes 
region. Beginning in the dec- 
ade 1820-1830 there was a large 
movement of population from 
New England and New York 
into the Lake region. For this 
there were many reasons, one of 
the most important being the 
great reduction in the expense 
and time involved in reaching 
the Interior, due to the opening 
of the Erie Canal in 1825 (p. 286) 
and the development of steam 
navigation on the western Lakes 
in the thirties. The first steamer 
appeared on Lake Ontario in 
1816, but not till ten years later 
did one enter Lake Michigan, 
and not until 1832 did one visit 
Chicago. As the number of 
steamboats increased, passenger fares decreased, and it was soon 
possible to take household goods, farming implements, and stock 
into the Interior easily and cheaply. 




Fig. 197. 

Fig. 196. Distribution of population 
in the Great Lakes region in 1830. 

Fig. 197. Distribution of population 
in the Great Lakes region in 1850. 



282 USES AND PROBLEMS OF INLAND WATERS 

A comparison of Figs. 196 and 197 will show how rapidly the nor- 
thern parts of Ohio, Indiana, and Illinois, and the southern parts of 
Michigan and Wisconsin were settled between 1830 and 1850. During 
this period, also, Buffalo, Cleveland, Toledo, Milwaukee, and Chicago 
had their first substantial growth. They served as points of contact 
between the agricultural Interior and the manufacturing and com- 
mercial East. Their prosperity depended on commerce; not till 
later did they come to have large manufacturing interests. 

The " Soo Canal " and the opening of Lake Superior. Be- 
fore the "Soo Canal" was opened in 1855 there was little commerce 
on Lake Superior, and for the most part its shores were an unsettled 
wilderness. The canal opened the borders of the lake to settlement, 
and permitted the development of their natural resources, especially 
the iron ore (p. 179) and lumber. The value of the canal was in- 
creased greatly in 1881, when the first enlargement was completed. 
Between 1880 and 1890, the population of the Lake Superior counties 
of Michigan, Wisconsin, and Minnesota increased respectively 90 
per cent, 400 per cent, and 800 per cent. The canal contributed 
greatly to this remarkable growth. In 1896, the canal was given a 
depth of 20 to 21 feet, and a further enlargement is now being made. 
There is also a Canadian canal around St. Mary's Falls. 

In recent years about Vz of the total traffic of the Great Lakes 
has passed in or out of Lake Superior through the "Soo Canal." 
The tonnage passing through it during the seven months of the open 
season is about four times as great as that passing through the Suez 
Canal during the entire year. About Vs of the freight which passes 
through the "Soo Canal" is east-bound. 

Traffic in iron ore and coal. In recent years the iron ore fields 
of the Lake Superior region have furnished about 4 /s of the output 
of iron for the whole country. Fig. 198 shows the movement of iron 
ore on the Great Lakes. Most of the ore goes to Lake Erie ports, 
and thence by rail to the Pittsburgh region. Most of the iron ore 
goes to the coal, rather than the coal to the iron, because the amount 
of coal needed in manufacturing steel is greater than the amount 
of iron ore, and because, where now manufactured, the steel is nearer 
its market than it would be if manufactured where the iron is mined. 
As Fig. 198 shows, much iron ore also goes to the iron and steel centers 
near the head of Lake Michigan, especially to South Chicago and 
Gary, Indiana. At these points Indiana and Illinois coal (see Fig. 85) 
may be obtained cheaply, and they are close to great markets. 



TRAFFIC OF THE GREAT LAKES 



283 



Many boats which bring iron ore, lumber, and grain to the east- 
ern lake ports take back coal at very low rates. This has helped 
to make possible the recent establishment of the iron and steel 
industry at the western end of Lake Superior. It also means cheap 




Fig. 198. Map showing movement of iron ore on the Great Lakes in 1909. 
(After Birkinbine.) 

coal in the region west of Lakes Michigan and Superior, which is 
without coal resources of its own. 

Lumber trade of the lakes. The western end of the great 
northern forest of pine, spruce, hemlock, cedar, fir, birch, etc., lies 
in Michigan, Wisconsin, and Minnesota (Fig. 271). Lumbering 
began in Michigan in the early thirties, and spread westward and 
northward. Production increased rapidly after 1850, and for many 
years the Lake states were the most important lumber district in the 
United States, furnishing, in 1880, ^3 of the total output of the 
country. Logs cut in the interior were floated down the streams to 
the Lakes. At the mouths of the larger rivers busy towns developed 



284 USES AND PROBLEMS OF INLAND WATERS 

where the logs were manufactured into lumber. First from the mill 
towns of eastern Michigan, and later from more distant points, the 
manufactured lumber was shipped at low lake rates to Detroit and 
the cities of Lake Erie. Most of the products of the Lake Michigan 
mills were sent through Chicago to the prairies, the settlement of 
which created a demand for enormous quantities of building and 
fence material. As the pine forests near the Lakes and along the 
larger rivers flowing into them were cut away, mill towns sprang 
up in the interior, from which more and more lumber and lumber 




Loading ore at Escanaba. (Copyright by Detroit Publishing Co.) 



products have been sent to market by rail. This change and the 
general decline of the lumber industry in the Lake region since 
1890 (p. 372), due to the cutting away of the forests, have reduced 
greatly the lumber trade of the Great Lakes. In 1910, 1,208,000 
thousand feet of lumber were transported on the Lakes. 

Movement of grain and flour. The transportation of grain 
and flour has been an important phase of commerce on the Great 
Lakes ever since the settlement of the Lake states. The movement 
is almost entirely from the south end of Lake Michigan and the 
west end of Lake Superior, to the east end of Lake Erie (Why?). 

Modern lake vessels. Much of the freight on the Great Lakes 
is carried in steel freighters, built for speed, capacity, and strength 
(Fig. 199). Many are 500 to 600 feet long, and have a capacity 
of 10,000 to 12,000 tons. One of the largest carried 13,000 tons of 



CANAL BUILDING IN THE UNITED STATES 285 

soft coal in a single cargo, and on another occasion 422,000 bushels 
of wheat. Another lake vessel transported more than 323,000 tons 
of iron ore in 27 cargoes during the season of 1907. 



CANALS 

General considerations. The first canal in the United States 
was opened in 1794, but there were few of importance until the 
successful completion of the Erie Canal (1825) aroused general 
interest in canals. The 
period of most active 
canal digging extended 
from 1825 to 1837. 
Altogether, about 4,500 
miles of canals have 
been constructed in the 
United States (Fig. 
200). Most of them 
extended and supple- 
mented natural water- 
ways. The more im- 
portant ones were of 
three classes: (1) Those 
along the Atlantic 
coast, connecting bays 
or rivers between which 
the natural water routes 
involved much greater 
distances. (2) Those 
connecting, or begun 
with the intention of 
connecting, the leading 
Atlantic seaports with the Ohio River or the Great Lakes. (3) Those 
connecting the Great Lakes with the Mississippi System. As Fig. 
200 shows, many feeders were built for the main canals. 

Of the 4,500 miles of canals constructed, nearly 2,500 miles, 
costing about $80,000,000, have been abandoned. Most of the con- 
ditions which contributed to the decline of river navigation (p. 278) 
contributed even more to the decline of the canals. They were all 
shallow, and the canal boats were therefore of small capacity; 
many of the canals varied in size in their different parts, retarding 



LA l( ^j£i 

-J \ J 1 PJ/4-- L 




—1 J;fct---4'-~-- 

! ! r \ «.. f 

\-\ | ) Y 




( o^ iA ^*~\/X \ 




\o\ 








Fig. 200. Map showing principal canals con- 
structed in the United States. Most of them are 
no longer used. 



286 USES AND PROBLEMS OF INLAND WATERS 

through traffic. Most of the canal boats were towed by animals. 
Some of the canals were located unwisely, some were managed badly, 
and most of them fell an easy prey to railroad competition. 

The Erie Canal. The Erie Canal, connecting the Hudson 
River with Lake Erie at Buffalo (Fig. 200), was built by New York 
to control the trade of the central and western parts of that state, as 
well as to gain the trade of the Great Lakes region, toward which 
settlement was setting. Some of the products of the former sections 
were going down the Delaware and Susquehanna rivers to Philadelphia 
and Baltimore, and some were seeking the Canadian markets along the 
St. Lawrence River. Such a canal was needed also for military 
reasons. In the event of another war along the northern frontier, 
some way better than any existing during the War of 181 2 was needed 
to get supplies to the shores of the Lakes. 

The canal became a great highway of expansion into the Inte- 
rior, and a great outlet for surplus western products; it caused the 
rapid growth of Buffalo, Rochester, and other places along its course; 
it increased land values throughout the region tributary to it; and it 
helped to transform New York City from a market town for the 
Hudson Valley into the leading commercial city of the continent. 
The cost of transportation between Albany and Buffalo fell from 
$88 to $5.98 a ton in the twenty-six years after the opening of the 
canal. The tolls collected on the canal paid for its construction in 
10 years. 

Until the late 1860's, the Erie Canal was the most important 
transportation route between the Great Lakes and the Atlantic 
Ocean. In 1866, the freight carried by the canal was 60 per cent of 
that moved across New York. Soon after this it began to decrease, 
and the tonnage on the canal has been small for years. The people 
of New York voted in 1903 to spend $101,000,000 in improving the 
canal, and this work is now in progress. 

Canals between Great Lakes and Mississippi System. It is 
impracticable to consider here, one by one, the different canals 
which connected the Great Lakes with the Ohio and Mississippi 
rivers (Fig. 200). In general, they injured the cities and trade 
of the Mississippi River (p. 277), and benefited greatly the cities and 
commerce of the Great Lakes. For a time, most of them were 
powerful factors in the development of the sections which they 
crossed. In addition to giving special benefits in different cases, they 
cheapened transportation, opened new markets, raised the prices of 



IMPROVEMENT OF WATERWAYS 287 

farm products, lowered the cost of imported merchandise, increased 
land values, stimulated the growth of population, and helped build 
up towns and cities. Some of these canals have been abandoned, 
and for years the rest have been used but little. 

Foreign canals. Several foreign countries have systems of 
canals suited to modern conditions of transportation. This is true 
particularly of Germany. One of the important canals of Germany 
(the Kiel Canal) was built to permit ships to pass between the Baltic 
and North seas without going around Denmark. The Manchester 
Ship Canal allows ocean-going ships to reach the docks of Manchester 
from Liverpool. 

IMPROVEMENT OF AMERICAN WATERWAYS 

Why waterways should be improved. The larger rivers of 
the United States should be so improved as to make possible eco- 
nomical transportation upon them. This is desirable because (1) 
water transportation is normally cheaper than rail transportation, 
and if the cost of transportation is reduced, the price to the consumer 
of the things transported will tend to be lower; (2) waterways tend to 
keep down the rates of competing railroads; and (3) in recent pros- 
perous years the railroads have been unable to handle promptly the 
traffic of the country during the busy season. The products and 
trade of large sections of the country are increasing much faster than 
the transportation facilities of the railroads. 

Leading improvements needed. Among the projected improve- 
ments are: (1) A deep canal (at least 20 feet) between the Hudson 
River and the Great Lakes. The new Erie Canal (p. 286) will have a 
depth of 12 feet. (2) A deep inner waterway along the Atlantic coast 
from New England to Florida, connecting various bays and sounds. 
(3) A deep waterway between Lake Michigan and the Gulf of Mexico. 
This involves extending the Chicago Sanitary and Ship Canal (built 
primarily to dispose of the sewage of Chicago) to the head of naviga- 
tion on the Illinois River, and improving the Illinois and Mississippi 
rivers. Such a waterway would be of great importance to the trade 
between the northern and southern parts of the Interior, and, follow- 
ing the opening of the Panama Canal (p. 355), to the trade of the 
northern Interior with the Pacific coast, and with foreign countries 
both to the south and across the Pacific Ocean. (4) A canal to connect 
Puget Sound and the Columbia River. 



288 USES AND PROBLEMS OF INLAND WATERS 



Water Power 

Use in the past in United States. Water power has located many 
manufacturing cities in the United States, and contributed largely 
to their growth. It was used first in a large way in New England, 
where it is one of the leading natural resources. Bellows Falls, 
Holyoke, Manchester, Lowell, Berlin, Biddeford, Lewiston, Rumford 
Falls, Augusta, and Bath are among the busy industrial centers 
created largely by water power. There are also many water power 
cities farther west. Grand Rapids, Michigan, a leading furniture 
manufacturing center, is an example. Located 40 miles inland, at the 
rapids of the Grand River, its first lumber mills were at a disad- 
vantage compared with those on the shores of the Lakes (p. 283; 
Why?). As a result, cabinet shops and furniture factories were soon 
established. (What was gained by doing this?) The power afforded 
by the river was soon outgrown, and the timber supply in the vicinity 
exhausted, but the advantages of an early start, and of established 
plants with world-wide reputations for furniture of superior quality, 
keep the city to the front. Similarly, St. Anthony's Falls and 
command of the forests and wheat-fields of Minnesota made Minne- 
apolis an important manufacturing city. Nearly Vio of the flour 
and grist mill products of the country are manufactured there. 

Water power formerly had certain disadvantages, because the 
mills using it had to be close to the source of the power. Coal was 
abundant, cheap, and easily shipped, and was used more and more 
for manufacturing purposes. Water power continued to be used 
most in connection with long-established industries, and in connec- 
tion with industries demanding special conditions, such as the manu- 
facture of paper and wood-pulp. 

Present conditions and future importance. In recent years 
there has been a great increase in the use of water power in the 
United States. In 1900, less than 1,500,000 horse power were devel- 
oped from water, and in 1908 more than 5,350,000 horse power. 
This change has been due largely to the following conditions, which 
also will help to bring about an increasing use of water power in the 
future: (1) There have been rapid developments in the transmission 
of energy in the form of electricity. Electric power developed by 
falls and rapids {hydro-electric power) is transmitted some 300 miles 
by a Colorado company. On the basis of transmission for 200 miles, 
a water power could, if sufficient, serve an area of 125,000 square miles. 



USE AND IMPORTANCE OF WATER POWER 289 

In the future, few places in the United States will be beyond the reach 
of hydro-electric power. Power from Niagara Falls now runs street 
cars, lights buildings, and is furnished very cheaply for manufacturing 
purposes in Buffalo and other cities as far away as Utica. On the 
Canadian side, it is carried to various cities and villages as far away 
as the Detroit River. Snoqualmie Falls, Washington, furnish power 
for electric lights, street railways, motors, etc., in Seattle and Ta- 
coma, some 50 miles distant. (2) In some ways, electric power is 
better than other kinds for large plants, and it also has a great ad- 
vantage over other forms of power in that it may be carried econom- 
ically to the small user. (3) In many places, hydro-electric power is 
even now cheaper than power obtained from coal. 

It ^estimated that about 3/^ of the power now developed from coal in the 
United States could be developed cheaper by water. Furthermore, the substitu- 
tion would lengthen greatly the duration of the coal supply (p. 177). 

As the supply of coal diminishes and its cost increases, electricity 
developed by water will be used more and more for transportation, 
lighting purposes, and manufacturing. Doubtless the time is not 
distant when most railroads, street cars, and interurban lines will 
be operated in this way. In time, nearly all manufacturing industries 
will depend largely on water power, and it is fortunate indeed for the 
future of the United States that its available water power is so great. 

Amount and distribution of water power in the United States. 
In view of the part which water power is to play in the life of the 
nation, its amount and distribution are matters of great interest 
and importance. The total amount has been estimated on several 
bases. (1) If the amount of water available in the streams during 
the two weeks of lowest water were used throughout the year, and 
if all above that amount escaped unused, about 37,000,000 horse 
power could be developed. This is called the primary horse power. 
(2) If plants were established to develop the minimum power avail- 
able for the six high- water months, there would be about 66,500,000 
horse power per year. (3) If the flood waters were stored in reser- 
voirs, so that the streams were utilized fully, there could be developed 
between 100,000,000 and 200,000,000 horse power. The meaning 
of these figures is realized best when it is remembered that now 
about 26,000,000 horse power are developed from coal, and only 
about 5,500,000 from water. The estimated distribution of water 
power throughout the country on the first two bases given above 
is shown in the table on the next page. 



2 9 o USES AND PROBLEMS OF INLAND WATERS 

ESTIMATE OF WATER POWER IN THE UNITED STATES 

Horse Power Available 
Prima rv nr Minimum of 
Principal Drainages MiSm the ? £ Highest 

Months 

Northern Atlantic to Cape Henry, Va 1,702,000 3,186,600 

Southern Atlantic to Cape Sable, Fla • . 1,253,000 1,957,800 

Eastern Gulf of Mexico to Mississippi River 559,000 963,000 

Western Gulf of Mexico, west of Vermilion River 433,760 822,650 

Mississippi River, main stream 147,000 335,ooo 

Mississippi River tributaries from east 2,472,590 4,940,300 

Mississippi River tributaries from west, including Ver- 
milion River 3,948,970 7,085,000 

St. Lawrence River to Canadian Line -6,682,480 8,090,060 

Colorado River, above Yuma, Ariz 2,918,500 5,546,000 

Southern Pacific to Point Bonita, Cal 3,215,400 7,808,300 

Northern Pacific 12,979,700 24,701,000 

Great Basin 518,000 801,000 

Hudson Bay 75, 800 212,600 

Total 36,906,200 66,449,310 

Improving water powers. It is highly desirable that power 
streams should maintain a relatively even flow. If a stream can 
develop 5,000 horse power during brief flood stages, and only 500 
horse power the rest of the time, not much more than the latter 
amount can be used, and the rest is lost. Forests about the head- 
waters of mountain streams and systems of reservoirs hold back 
the storm-waters and tend to keep the flow of streams steady. They 
are therefore important to manufacturing, as well as to navigation and 
farming (pp. 166-169, 221-222). 

Water power in other countries. Water power is afforded 
by most large streams in mountain regions, and by many youthful 
streams in other regions, especially those that have been glaciated 
recently. In Europe, Switzerland is likely to be the first country 
to utilize fully its large water power resources. The streams of 
Scandinavia, Austria-Hungary, France, Italy, and Germany also 
afford much power. Enormous power could be developed from the 
streams of the Caucasus and Himalaya mountains, but this is not 
likely to be done in the near future. Considerable power may be 
obtained from the streams of eastern Australia. Canada has an 
abundance of water power, both in the western mountains and in 
the eastern part of the country. In the latter section, it is due 
largely to glaciation. Many other countries have more or less 
water power, much of which will be of value to man sometime, if 
not so now. 



WHY IRRIGATION IS PRACTICED 291 

Irrigation 

Irrigation means the artificial application of water to land for 
the benefit of plants. It is practiced in many dry regions because 
otherwise crops cannot be grown, and it is being introduced more 
and more into humid regions, in order to increase the yield of crops. 
Even in eastern United States, there is scarcely a year when some 
crops do not suffer from lack of rain, and there are occasional years 
of serious droughts. 

The common statement that farming without irrigation cannot be 
carried on successfully where the annual rainfall is less than twenty 
inches is very misleading. The development of "dry farming" 
(p. 329) and the introduction of drought-resisting plants (p. 173) are 
changing some semi-arid regions into fairly productive farm lands, 
without irrigation. Again, much depends on the distribution of the 
rainfall. If it came just when the plants needed it, ten or twelve 
inches would suffice to grow many staple crops by ordinary methods 
of farming. The yields that would be obtained under such conditions 
could be increased greatly, however, by irrigation. 

Practiced since ancient times. Irrigation was practiced in 
Egypt 2,000 years before Christ, and probably much earlier, but the 
area irrigated then was much less than now. About 6,000,000 acres 
have been irrigated in Egypt in recent years. The ancient civiliza- 
tions which existed in Mesopotamia were made possible by extensive 
systems of irrigation. The ditches of the region have long been 
unused, and much land which once was cultivated is now waste. 
The English government has extended irrigation in India until about 
50,000,000 acres are so watered. 

IRRIGATION IN WESTERN UNITED STATES 

Irrigation was practiced first in the United States in Arizona 
and New Mexico. In the latter, there are ditches said to have 
been used continuously for 300 years by people of mixed Span- 
ish and Indian descent. The Mormons were the first Americans 
(except Indians) to irrigate systematically. The conditions for 
irrigation were ideal on the slopes of alluvium at the base of the 
Wasatch Mountains, and without irrigation they could not have 
been cultivated. Irrigation by Americans in the Salt River Valley 
of Arizona began in 1867, and in southern California a few years 
later. 



2 9 2 USES AND PROBLEMS OF INLAND WATERS 

Value of irrigated land. Irrigation changes unproductive, 
worthless, or nearly worthless land into land producing more than 
the average farm land in eastern United States. (Compare Figs. 




Fig. 20 1. The Yakima desert before irrigation. Near North Yakima, 
Washington. (U. S. Reclamation Service.) 



* \n 










< 
\Bfc> 

K 






WS&' 



Fig. 202. The region shown in Fig. 201, after irrigation. (U. S. Reclama- 
tion Service.) 



VALUE OF IRRIGATED LANDS 



293 



201 and 202.) Irrigated lands are worth $100 or $150 an acre for 
general farming purposes, and choice fruit lands with good orchards 
are worth $1 ,000 or more an acre. In general, the great value of much 
of the irrigated land is due to the following: (1) The soil of arid regions 
is likely to be rich in mineral plant foods, because for ages ground- 
waters have come to the surface through capillary action, and as 
they evaporated into the dry air they have deposited in the soil the 
mineral matter dissolved 
during their journey un- 
der-ground (p. 212). In 
some cases when irrigating 
waters have been turned 
on the land it has been 
found that so much of 
certain materials (alkaline 
salts or "alkali") had ac- 
cumulated in this way in 
the soil, that plants would 
not thrive until the alkali 
was partly leached out. 
(2) Irrigated soils, when 
used rightly, are durable, 
for soil wash can be avoid- 
ed largely, and the store 
of soluble mineral matter 
in the sub-soil is large. (3) 
Irrigating waters contain 
fertilizing matter in solu- 
tion. (4) Irrigated crops, 
if properly cared for, get 
just the amount of water 



II 

b 


Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec 
























6 
















18 


95 






4 






















2 
































































7R 
























54 
























50 
























26 
























22 
























18 










i 














14 










1 






18 


96 






10 










1 


1 












8 








. 


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1 












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1 


, 


rm 












4 






"1 


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2 






J 


im, 














a 


tatf 


J 


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Fig. 203. Diagram showing discharge of 
the Boise River above Boise, Idaho, in 1895 
and 1896. (Newell, U. S. Geol. Surv.) 



needed at just the time they need it. (5) In the warmer sections of 
the West, several crops a year may be grown. 

Area of irrigable land. As the demand for land increases with the 
population, it will be advisable to extend irrigation to the utmost 
limit. It is estimated that about 45,000,000 acres (an area the size of 
Missouri) are irrigable. This is only about 5 per cent of the entire arid 
region. The chief factors which will control the area which can be 
irrigated are matters of topography and rainfall. (1) The water 
supply comes largely from rain and snow falling on the mountains, 



294 USES AND PROBLEMS OF INLAND WATERS 



and the mountain catchment areas are comparatively small. Further- 
more, only a small fraction of the rainfall of the arid region can be 
made available for irrigation (Why?). (2) The volume of many of 
the western rivers varies greatly (Why? Fig. 203), and in many cases 
it is necessary to build dams to hold the flood waters in reservoirs, so 
that they may be let out as needed during the growing season. Un- 
fortunately, there are comparatively few places suited for the storage 

of large amounts of 
water, and in some cases 
where there are good 
sites for dams, the areas 
tributary to them furn- 
ish little water. (3) In 
many places the ground 
is so rough that the 
water cannot be spread 
over it properly. (4) In 
many places the possible 
crops probably would 
not justify the expense 
of getting the water on 
the land. (5) The area 
which can be irrigated 
depends in part upon 
the amount of water per 
acre required for crops. 
In the case of the gov- 
ernment projects (p. 295), this varies from i}£ to 5^ acre-feet 1 
per year. (Apart from the fact that some crops require more water 
than others, why should the variation be so great?) 

There are several reasons for hoping that the irrigable areas may 
prove larger than stated above. (1) Many fields are now poorly 
prepared for the water, so that it spreads unevenly, and more is 
required than would be if the land were less uneven. With the 
land better prepared, the water could be spread over a larger area. 
(2) Much more land could be watered if loss by seepage from the 
canals were not so great. This now amounts, on the average, to about 
25 per cent of the water. The loss probably will be reduced more 

'An acre-foot of water is the amount which would cover an acre of ground to 
the depth of one foot. 




Fig. 204. A canal lined with cement. Truckee- 
Carson Project, Nevada. (U. S. Reclamation 
Service.) 



GOVERNMENT IRRIGATION PROJECTS 



295 



and more by lining the canals with cement (Fig. 204). (3) The loss 
of water by evaporation from the canals also will be reduced. (4) 
Many irrigators now use much more water than is necessary to 
secure the largest returns. This will be corrected by legislation, 
and by increasing intelligence on the part of the farmers. (5) Meas- 
urements to determine the amount of available water have been made 




Fig. 205. Map showing Government irrigation projects. 

on only a part of the western streams, and on most of these the 
records cover only a few years. Further work along this line may 
show that the streams can furnish more water than is now supposed. 
(6) For much of the West detailed topographic surveys have not been 
made, and they may add new possibilities. 

Government projects. Irrigation was begun in the West by 
individual settlers, who led water to their fields from small rivers and 
creeks through ditches which they dug. Co-operation was necessary, 
however, before extensive areas could be watered. This has been 
brought about in various ways. Many so-called "irrigation districts " 
have been organized to reclaim arid land under state laws. Since 



296 USES AND PROBLEMS OF INLAND WATERS 



1894, much land has been reclaimed, especially in Idaho and 
Wyoming, under the Carey Act, which provides for irrigation 
through co-operation by the nation, state, corporations, and settlers. 
While much was being accomplished in these ways, it became evident 
that the federal government must itself undertake those projects 
that were too expensive, too large, or too slow in producing returns, 
to tempt individuals or companies. Hence Congress passed the 
National Reclamation Act in 1902. This act provides that money 

derived from the sale of 
public lands in the arid 
states shall constitute a 
reclamation fund. The 
cost of any given project 
is assessed against the 
land benefited, and is 
paid by the settlers in 
ten equal annual pay- 
ments. The moneys 
returned to the govern- 
ment, together with the 
proceeds of the sale of 
other lands, are used 
again for further recla- 
mation. 

There are some thirty government projects under way (Fig. 205), 
which, when finished, will irrigate more than 3,000,000 acres. The 
average cost to the settler probably will be $40.00 to $50.00 per 
irrigated acre. The success of these great projects of the government 
has stimulated private enterprise greatly. 

A few facts concerning some of the government projects will illus- 
trate the scope of the work. The Salt River Project (Arizona) has 
the recently completed Roosevelt dam, 280 feet high and 1080 feet 
long on top. This dam forms a lake covering 16,320 acres. The 
power developed by the water as it comes out is used to pump ground- 
water to irrigate more land, for lighting purposes, and in other ways. 
The storage dam for the Rio Grande Project is one of the largest in the 
world. It will make a lake 40 miles long, covering 40,000 acres, and con- 
taining 2,600,000 acre-feet of water. The water for the Truckee- 
Carson Project (Nevada) is stored in Lake Tahoe, a glacial lake 
in the Sierra Nevada Mountains. From Truckee River, the out- 




Fig. 206. Site of the great dam on the Sho- 
shone River, in Wyoming. 



PRODUCTS OF IRRIGATED LANDS 297 

let of the lake, it is diverted into a canal and carried across to the 
Carson Valley to reclaim land formerly composed largely of sand 
dunes and alkali flats. Nearly half the area of the Klamath Project 
(California-Oregon) is occupied by swamps and lakes, so that it 
must be drained before it can be tilled. After being drained, it will 
need to be irrigated. The water supply for the Shoshone Project, 
in northern Wyoming, is derived from the Shoshone River. To 
regulate the flow of this river, the government has built a dam 328^ 
feet in height (Fig. 206), the highest structure of the kind ever built. 

Crops of the irrigated lands. Many different crops are grown 
on the irrigated lands, for the conditions affecting plant life vary 
greatly. Alfalfa and sugar beets are produced in many places. Hay, 
grain, and vegetables are staple products in Montana and Wyoming. 
In addition to these things, fruits are grown extensively in Idaho, 
Washington, Oregon, and Colorado. The great citrus fruit region is 
in southern California, and the raising of these fruits has increased 
rapidly in recent years. In 1910-n, nearly 18,000,000 boxes of oranges 
and lemons were shipped. The growing of deciduous fruits (peaches, 
pears, and the like) also has become of great importance in California, 
as in various other sections of the West. The shipping of these fruits 
in large quantities to distant markets has been made possible by the 
development of the refrigerator car, in which most of the shipments 
from California are made. In the extreme southwest, the leading 
products are semi-tropical fruits, cereals, and alfalfa. 

Population capacity of the irrigated lands. The high value 
of the irrigated lands encourages methods of tillage which secure 
maximum yields from minimum areas, and, together with the diffi- 
culty of hiring effective labor in the West, leads to small farms. In 
orchard regions, 5 to 10 acre holdings are common. On a number 
of the government projects, the farm unit has been fixed at forty acres. 
These things mean a dense rural population. The ultimate popula- 
tion of the irrigated lands probably will be not far from one person to 
an acre. 

Farm villages. In many ways, social conditions promise to 
be nearly ideal in most of the irrigated districts. The small farms 
will make it possible for many of the farmers to live in town, going 
to and from their land daily. It seems probable that each 5,000 or 
6,000 acres of cultivated land will support a farm village, where the 
farmers will have the advantage of graded schools, public libraries, 
etc. On a number of the government projects, the Reclamation Serv- 



298 USES AND PROBLEMS OF INLAND WATERS 

ice has laid out town sites about six miles apart, and set aside lots 
for churches, schools, and cemeteries. The town lots are sold to 
the highest bidders, the proceeds going to the Reclamation Fund. 
Irrigation promises to create many small villages, rather than a few 
large cities. 

Irrigation and the National Forests. From the standpoint of 
irrigation, as well as of navigation and water power, it is highly impor- 
tant that the flow of the streams be uniform. The preservation 
of forests about the headwaters of the streams helps to bring about a 
more even flow of water, and partly for this reason the National 
Forests were established (Fig. 207). Outside Alaska, these forest 
reserves have an area (191 2) of about 144,000,000 acres. They are 
cared for by the Forestry Bureau of the Department of Agriculture. 

IRRIGATION IN THE HUMID STATES 

Present situation. Irrigation is practiced in some of the humid 
states in growing certain crops. For example, water is pumped 
from wells on to the land at various points on the coastal plain between 
New Jersey and Florida, to irrigate truck farms. In the latter 
state, irrigation has been undertaken recently on a rather large 
scale. This is particularly interesting, since all parts of Florida 
receive more than 50 inches of rain a year, and some parts more 
than 60 inches. But much of the soil does not retain moisture well, 
evaporation is great, and the fruit groves and truck farms are bene- 
fited by watering during the drier season. Their products are so 
valuable that even a partial crop failure means heavy losses. Irri- 
gation is practiced extensively on the rice-fields of Louisiana, Texas, 
and the Carolinas. 

As yet, irrigation in the East is restricted largely to special crops 
which warrant relatively large expenditures, such as strawberries, 
raspberries, blackberries and other fruits, and certain vegetables. 
With these crops, a small or imperfect yield because of drought is 
disastrous. 

Future importance. It has been estimated that the yield 
of every important crop of eastern United States could be doubled 
by irrigation. It is therefore certain to be practiced more and more 
in the future, as the population increases and the demand for food 
grows. As in the West, the irrigator can apply just the amount of 
water needed at just the time required, and he can grow many more 
plants on an acre than otherwise. 



THE NATIONAL FORESTS 



299 




3 oo USES AND PROBLEMS OF INLAND WATERS 

Reclamation or Swamp and Overflowed Lands 

WET LANDS OF THE UNITED STATES 

The reclamation of swamp and lake areas has been referred to 
incidentally in other connections (pp. 171, 241, 242, 262). The 
matter is summarized briefly here. 

Area and distribution. It is estimated that the total area of 
swamp land in the United States is about 79,000,000 acres, most of 
which can be reclaimed ultimately. Swamp lands occur in many 
states, but the largest areas are in the states containing (1) the 
Atlantic and Gulf coastal plains, (2) the flood-plains of the Mississippi 
River and its larger tributaries, and (3) the area covered by the 
last ice-sheet. About half of all the area of swamp land is in Florida, 
Louisiana, Mississippi, and Arkansas. 

Status and cost of reclamation. It is estimated that nearly 
16,000,000 acres have been drained, mostly in the northern interior 
states. In most other parts of the United States, the problem of 
draining wet lands received little attention until the last few years. 
This was due to the abundance, till recently, of good land not re- 
quiring drainage. Progress is now being made in Florida, Louisiana 
(p. 171), and other states. 

The cost of reclamation varies with the character of the swamp, 
the methods employed, and the machinery used, from $3 or so an 
acre, to $30 or more. In some cases ditches to carry off the water 
are all that is needed, and the cost is then slight; in other cases tile- 
draining is necessary, and then the cost depends largely on the 
character of the land. Along many rivers and coasts it is necessary 
to build dikes. The water of the swamps is then brought to certain 
points by drains or ditches, and pumped out over the dikes. In 
many such cases, rather large areas are treated as units, and improve- 
ments in methods and machinery have reduced the cost one-half 
in the last 15 years. The average cost of drainage has been estimated 
at $15 an acre. This is much less than the average cost of irrigating 
dry lands (p. 296). 

Results of reclamation. (1) The soils of most reclaimed swamp 
lands are very fertile. Since most swamp areas are of little use, it is 
clear that drainage greatly increases their value. 

The value of drained farming land varies from $20 or less an acre, to $500 
and more. It depends largely on the character of the soil, the climate, transpor- 
tation facilities, nearness to or distance from good markets, etc. It has been 



RECLAMATION OF WET LANDS 301 

estimated that, when drained, the swamp lands of the United States will have an 
average value of $60 an acre. Their present value has been estimated at $8 an acre. 

(2) The products of the drained lands will increase greatly the 
crops of the country, and will feed and support millions of people. 

(3) An immediate effect of the systematic draining of the swamp 
lands will be to increase the healthfulness of the areas concerned. 
The principal breeding places of malaria-carrying mosquitoes will 
be destroyed, and that disease practically stamped out. The present 
annual loss to the country from malaria, due to the reduced efficiency 
of the sufferers, the losses to business in the areas affected, etc., has 
been estimated at $100,000,000. 

Reclamation of lake-covered lands. Swamps merge into lakes, 
and many so-called lakes doubtless are included in the estimate of 
swamp areas already given. Ultimately, most shallow ponds and 
lakes will be drained. It will always be impracticable to drain some 
lakes, and many others will be carefully protected and preserved 
(p. 264). 

WET LANDS OF OTHER COUNTRIES 

Large areas of wet land have been reclaimed in Europe. Much 
land now farmed in Holland was won from the sea. About y$ of 
England was marsh or bog land in the reign of Alfred the Great (871- 
901). Probably " not far from V20 of the tillable land in Europe was 
inundated and unfit for agriculture in the eighth century of our era." 

Vast areas of swamp land in various tropical countries probably 
will remain in their present condition for a long time. 

Water Supply 

Apart from its support of plant and animal life, the most impor- 
tant use of water is for home and city purposes — that is for drink- 
ing, bathing, and various household purposes, for sprinkling streets, 
flushing sewers, for fire protection, manufacturing, and the like. It 
is estimated that between 50 and 150 gallons of water per person are 
used daily in the cities of the United States. Of this, about half 
a gallon per person is used for drinking. 

Sources of water supply. (1) Rain-water, stored in cisterns 
and "tanks," is used extensively for drinking in the arid states, and 
for other purposes throughout much of the country. (2) Most of 
the country people of the United States obtain water for domestic 
purposes from underground, through ordinary wells and springs; but 



3 o2 USES AND PROBLEMS OF INLAND WATERS 

no large city could get water enough in this way. Thousands of 
wells and springs have failed in recent years because the water table 
(p. 205) has been lowered by unwise farming and deforestation (p. 208). 
(3) In the Atlantic Coastal Plain, the Great Plains, and some other 
parts of the country where the arrangement and position of the 
rock strata are favorable, artesian wells (p. 209) supply large amounts 
of water. 

Sand and gravel are in general good water bearers, while clay yields relatively 
little water (Why?). Many wells sunk in the glacial clays of northern United 
States obtain their water chiefly from beds or pockets of sand and gravel in the drift. 
Among the solid rocks, sandstone is a good water carrier, because it is porous, and 
shale a poor one, because it is compact. Granite and many similar rocks are 
dense, and hold little water, the largest supplies being found in cracks and other 
openings in the rocks. 

(4) Thousands of lakes, particularly in the glaciated parts of the 
country, may serve as sources of water supply for neighboring cities 
and villages, and many are so used now. From the Great Lakes or 
their connecting rivers, Buffalo, Cleveland, Detroit, Milwaukee, 
Chicago, Duluth, and many smaller cities get their supply of water. 
(5) Many villages and cities get their water from streams. Thus 
New York City's supply is from streams and reservoirs in the Catskill 
Mountains and the uplands east of the lower Hudson River; Phila- 
delphia depends on the Delaware and Schuylkill rivers, Cincinnati on 
the Ohio, Minneapolis and St. Louis on the Mississippi, and Omaha 
and Kansas City on the Missouri. 

In recent years various cities have outgrown their supplies of water and have 
had to seek new supplies, in some cases at considerable distances and at great 
expense. Los Angeles is expending more than $25,000,000 in this way. Water 
is to be brought from Owens River, across the Mojave Desert and through the San 
Bernardino Mountains, in an aqueduct of steel and concrete some 240 miles long. 
New York City is expending nearly $100,000,000 to obtain an additional supply of 
500,000,000 gallons a day from the Catskill Mountains, more than 80 miles away. 

Quality of waters. Drinking water should be reasonably 
clear, tasteless, and free from germs of disease. Some cities have 
expended large sums to guard the purity of their water. Some 
of them have bought large tracts of land, with their lakes, springs, 
and other stream sources. The waters of these tracts are then 
protected carefully from contamination, and carried to the cities in 
ways that prevent pollution on the way. Other cities have estab- 
lished filtering plants through which all the city water passes before 



WATER SUPPLY PROBLEMS 303 

use. Nevertheless, the use of impure drinking water is still a leading 
cause of disease in the United States. Many wells receive drainage 
from barnyards and cesspools (p. 207), many springs used as a source 
of drinking water are exposed to surface wash and to pollution by 
stock, and many villages and cities use river and lake water con- 
taminated by sewage. 

For many industrial purposes, the value of water depends on 
the kind and amount of mineral matter it contains. Distilleries 
and breweries require water of exceptional purity. Laundries and 
textile mills need water which is clear, free from iron, and contains 
little other mineral matter. Railroad companies spend large sums 
in treating the waters used in their engines, so as to make them 
less injurious to the boilers. Knowledge of the quality of the waters 
of the country is so important for various reasons that extensive 
investigations of surface and ground waters are being made by the 
United States Geological Survey, and by various state and private 
agencies. 

Questions 

1. Are cities more likely to develop on the inside or outside of great bends on 
navigable rivers? Give examples and reasons. 

2. Why does the cost per ton for transportation by water tend to decrease 
as the size of the cargo increases? 

3. Why are four-fifths of the population of New York state in the counties 
bordering the Hudson River and Erie Canal? 

4. (1) Account for the enormous amount of water power available in the 
Northern Pacific district, according to the table on page 290. (2) Why do the 
western tributaries of the Mississippi River afford more power than the eastern 
tributaries? (3) Why does the Northern Atlantic district (p. 290) furnish more 
water power than the Southern Atlantic? 

5. Explain the fact that apples and other fruits are grown in great perfection 
and abundance on irrigated lands around Grand Junction, in western Colorado, 
while in the same latitude in western Nevada attention is given largely to hardier 
crops, such as grain and potatoes. 

6. Account for the fact that legislation concerning the utilization of stream 
and ground waters is more advanced in western than in eastern United States. 



CHAPTER XVII 

MOUNTAINS AND PLATEAUS AND THEIR RELATIONS TO 

LIFE 

Mountains and plateaus have been referred to frequently in 
earlier pages. The more important points concerning their origin, 
their history, and their relations to human affairs are considered 
in this chapter. 

Mountains 

Distribution of mountains. As already noted, mountain ranges 
are situated in general toward the borders, rather than in the interiors, 
of the continents, and most of the longer and higher systems are not 
far from the edges of the greatest ocean basin. The settling of the 
ocean basins, due to the shrinking (partly through cooling) of the 
earth, may have been an important cause of the uplifts which have 
made mountains near the edges of the continents. 

Leading types of mountains, (i) Fig. 208 shows several moun- 
tain ridges of one type, and suggests their origin. A plateau or plain 

was divided by giant cracks 
into a series of great blocks, 
which were displaced {faulted), 
the relatively elevated edges 
forming mountain ridges. The 
mountain ridges may be due to 
uplift, or to the sinking of the 
lower land adjacent to them, 
or to both. Such mountains 
are called faulted or block mountains. Block mountains in various 
stages of dissection occur in Oregon, Nevada, and elsewhere. 

(2) Mountains consisting of a series of folds formed by com- 
pression from the sides are a common type. In some cases the folds 
are open and regular (Fig. 209) ; in others they are closed, irregular, 
and overturned. In some cases the strata of the folds are faulted 




Fig. 208. Diagram of block moun- 
tains. (Modified after Davis.) 



304 



LEADING TYPES OF MOUNTAINS 



3o5 



(Fig. 210), and some of the faults record a vertical displacement of 
thousands of feet. The present topography of most folded moun- 
tains — for example, of the Appalachians and Juras — is controlled not 



Fig. 209. Open, symmetrical folds in the Appalachian Mountains. North- 
eastern West Virginia. Length of section, about i2>£ miles. The formation 
shown in solid black contains coal. (After U. S. Geol. Surv.) 

so much by the original folding and faulting as by later erosion 
and warping. 

(3) Many of the higher isolated mountains are volcanic cones 
(p. 193; Fig. 99). Many mountains have been formed also by great 




Fig. 210. Folded and faulted strata in the Appalachian Mountains near 
Bristol, Virginia. (After U. S. Geol. Surv.) 



intrusions of lava which have domed or lifted the overlying beds high 
above the level of the surrounding country (Fig. 105). In many such 
cases the rocks which covered the lava have been partly removed 
by erosion, exposing the core of intruded rocks (Fig. 211). Among 
the mountains produced chiefly 
by vulcanism and later erosion 
are the Henry Mountains of 
Utah, and the Park and Elk 
ranges (Fig. 212) of Colo- 
rado. 

(4) Many mountains owe 
their existence simply to the 
resistance of their rocks, which 
have been left standing in bold 
relief by the removal of the sur- 
rounding weaker rocks. Many 
mountain peaks, aside from vol- 
canic peaks, are of this origin. Fig 2I2 Cross-section of Elk Moun- 

Pike s Peak, Colorado, is a tains, Colorado. 




Fig. 211. An eroded laccolith. Cross- 
section of Mount Hillers, Utah, with ideal 
representation of the underground struc- 
ture. Compare with Fig. 105. (After 
Gilbert, U. S. Geol. Surv.) 



3 o6 MOUNTAINS, PLATEAUS, AND LIFE 

well-known example. The Catskill Mountains of southeastern New 
York are due to unequal erosion, where the resistance of the rock 
is not very unequal. They are really a dissected plateau. Various 
other maturely dissected plateaus of considerable relief are called 
mountains. 

(5) Folding and faulting, vulcanism and unequal erosion all 
may be involved in the formation of lofty mountains. Many moun- 
tains, furthermore, have had several periods of growth, between 
which the upraised beds suffered great erosion (Fig. 213). 

The formation of mountains is a very slow process, probably 
occupying, for the greater ranges, hundreds of thousands or even 




Fig. 213. Diagram showing structure of the beds in the region of the Santa 
Lucia Range, California. Length of section, about 11 miles. (After U. S. Geol. 
Surv.) 

millions of years. Many mountains appear to be growing now — 
for example, the St. Elias Range of Alaska. 

Destruction of mountains. All mountains are destroyed in time 
by erosion, unless renewed by vulcanism or uplift. Furthermore, 
the erosion of mountains commences as soon as they begin to rise, and 
continues throughout the long period of their growth, as well as after- 
wards. As a result, no mountain due to vulcanism or diastrophism 
(crustal movements) ever had the full height which those processes 
would have given it, if there had been no erosion. As already 
pointed out, many mountains have been nearly or wholly removed 
by erosion, and revived again by uplift, and some of them have 
passed through this history several times. The length of the life 
of a mountain which has ceased to grow is determined largely by 
its height, by the resistance of its rocks, and by the character of the 
climate. 

The gentle slopes of the later life of a mountain are worn less 
rapidly than the steeper slopes of its earlier career, so that its old age 
may be longer than its youth and maturity combined. All lofty 
mountains are rather young, geologically speaking; old mountains 
have been worn low. While very old mountains are low, obviously 
not all low mountains are old. 



MOUNTAINS AS BARRIERS 



307 



Mountains as barriers. Mountains are barriers to the move- 
ment of animals and men, and to the spread of plants (Fig. 214). 
The effectiveness of a mountain barrier depends largely on its height, 
length, and width; on the number, height, and distribution of the 




Fig. 214. Toltec Gorge, in the mountains of Colorado. Travel even along 
the valley is difficult. (Denver and Rio Grande Railroad Company.) 



passes; and on the number of ridges, and the steepness and character 
of their slopes. The high, massive ranges of the Pyrenees, Caucasus, 
and Andes mountains form very effective barriers. The Pyrenees 
make the best natural inland boundary in Europe, shutting off Spain 
so completely from the rest of the continent that it has been said: 
"Africa begins at the Pyrenees." Although high, the Alps Moun- 



3 o8 



MOUNTAINS, PLATEAUS, AND LIFE 



tains have several good passes, well distributed; accordingly, they 
form a less serious barrier. The effect of many mountain barriers 
has been lessened by the building of wagon roads and railroads, 
the cutting of tunnels, etc. In other cases, mountains are crossed 
only by a few difficult trails, along which wares are taken on pack 
animals or by human carriers. 

For a long time, northern and central Europe was excluded by mountains 
from the culture of the leading Mediterranean countries. China is largely shut 
off from the rest of Asia by mountains, a fact of much importance in connection 
with the isolated development and backward state of that country. The Appa- 
lachian barrier helped to confine the English colonies to the Atlantic seaboard for a 
century and a half. This favored the development of compact settlements, and 
permitted much more rapid progress along many lines than would have been 




Fig. 215. Map showing course of Cumberland National Road. 



possible had the colonists spread themselves thinly over a vast area, after the 
manner of the French, who controlled the St. Lawrence gateway into the Interior. 
For years after the Revolutionary War, the Appalachian Mountains made commu- 
nication difficult between the settlements of the Interior and the seaboard. The 
first great step in their conquest as barriers to trade and travel was taken when the 
Cumberland National Road was completed from Cumberland, Maryland, to the 
Ohio River at Wheeling, in 181 7 (Fig. 215); the second when the Erie Canal was 
opened (1825). Though this canal did not cross the Appalachians, it afforded an 
easy route to the Interior. The third and greatest step in the conquest of the 
mountains was taken when four railroads were finished across them in the 1850's. 
These first trans-Appalachian railroads crossed the barrier at the north, where it is 
narrowest, lowest, and has most good passes. Until the completion of the first 
transcontinental railroad (1869), travel across the western mountains and plateaus 
was so difficult that many people going to California chose the 13,000-mile voyage 
around Cape Horn, or the route by way of Panama. 

The difficulty of crossing high, rugged mountains gives great 
importance to notches or passes in their ridges. Many mountain 
passes are water-gaps or wind-gaps; their formation has been ex- 
plained, and their relation to human affairs illustrated (pp. 232, 234). 



IMPORTANCE OF MOUNTAIN PASSES 



309 



Trails, wagon roads, and railroads all seek the lowest and most acces- 
sible passes (Fig. 216). They commonly enter the mountains along 
main valleys, and, where necessary, zigzag up the steeper slopes to the 
passes which serve as gateways through the central ridges (Fig. 217). 
In some cases, railroad companies have avoided the last part of the 
ascent by tunneling the 
mountain below the 
pass. 

South Pass, in central 
Wyoming, is the most im- 
portant pass, historically, 
in the Rocky Mountains. 
Through it ran the famous 
Oregon Trail, along which 
many thousands journeyed 
to the grain lands of Oregon 
and the gold fields of Cali- 
fornia. Truckee Pass af- 
fords a relatively easy route 
across the central part of 
the Sierra Nevada Moun- 
tains. It was used first by 
the California Trail, and is 
used now by the Southern 
Pacific Railroad. The Pass 
of Belfort, between the 
Vosges and Jura mountains, 
connects the Rhone and 
Rhine valleys, and with 
them has constituted since 
ancient times one of the 
most important routes of 

travel between the Mediterranean and North seas. The passes in the mountains 
of northwestern India have served repeatedly as gateways through which tribes 
and armies from central Asia have descended to plunder and conquer the people of 
the plains. 

The difficulties of travel and communication in rugged moun- 
tains shut their inhabitants away from the outer world, helping 
to retard progress. Old customs, fashions, and manners of speech 
are likely to be preserved by mountaineers long after they have 
been abandoned elsewhere. Education is backward; much of the 
simple clothing, furniture, etc., is home-made; trade in many cases 
is limited to barter, involving only the absolute essentials of life; and 
social intercourse is restricted seriously, favoring the close intermar- 




Fig. 216. Sketch-map of region about Holli- 
daysburg, Pennsylvania, showing the influence of 
mountain passes upon the course of wagon roads 
and railroads. (From Hollidaysburg. Sheet, U. S. 
Geol. Surv.) 



3io 



MOUNTAINS, PLATEAUS, AND LIFE 



riage of families and the development of " clans." These conditions 
are illustrated among the mountaineers of the southern Appalachians 




Fig. 217. Road zigzagging up mountain slope in Switzerland. Rhone Glacier 
in middle background. 

(Fig. 218). They do not exist, of course, in new mountain commu- 
nities established by progressive people from outside, and they have 




Fig. 218. Homes of mountaineers in the southern Appalachians. 

been changed greatly in some long-settled mountains (e. g., in the 
Alps) by the coming of summer visitors (p. 317), and in other ways. 



THE SETTLEMENT OF MOUNTAINS 311 

Many mountains are important climatic barriers (p. 77), and 
the conditions of life on their opposite sides may be very different. 
The western slopes of the Sierra Nevada Mountains receive much 
rain; to the eastward stretch broad deserts. Because most of its 
early mines proved disappointing, and lack of rain prevented ordinary 
farming in most places, the population of Nevada was always small 
(only 42,000 in 1900). This was the penalty of its position to the 
leeward of high, rain-catching mountains. Recently the population 
of Nevada has increased (p. 330) because of irrigation and the dis- 
covery of new mineral wealth. The contrast is even greater between 
the two sides of the Himalaya Mountains; to the south are the 
crowded millions of India, to the north the scattered, nomadic tribes 
of Tibet. The difference here is not due wholly to the mountains, 
but largely to the great altitude of the plateau on the northern side. 

The settlement of mountains. In general, the settlement of 
rugged mountains begins only after the more inviting neighboring 
lowlands have been occupied, and their populations are always rela- 
tively sparse. The areas of the Adirondack, Catskill, Alleghany, 
and other mountains in eastern United States were blank spaces on 
the earlier census maps (Figs. 276 and 278), and their populations 
are in most sections sparse even now (Fig. 281). A similar situation 
exists in the western mountains. 

Mountain areas are settled first and most thickly in their larger 
valleys. Here the flatter land favors tillage, soils are thicker and 
in most cases more fertile (Why?), the climate is milder, and the 
trails of the upland are replaced by roads. 

The inhabitants of many mountain valleys in Europe and Asia are descendants 
of people who sought refuge there from their enemies. The Basques, who dwell 
in the western valleys of the Pyrenees, are an example. In other cases, the occupa- 
tion of mountain strongholds has permitted people to dominate the adjoining 
lowlands, and levy tribute on their inhabitants. At the beginning of the Revolu- 
tionary War. four-fifths of the Cherokee Indians dwelt within the southern Appa- 
lachians, and from their mountain villages they repeatedly made sudden attacks 
on the frontier outposts of the whites. 

Agriculture in mountains. Outside the valley bottoms, con- 
ditions are unfavorable to agriculture in high mountains, and in 
many places prevent it. Many slopes are too steep to be tilled, 
consisting either of bare rock or having here and there a thin covering 
of soil which washes easily when cultivated; and with increasing 
height, the climate prevents the raising of crops and even the growth 
of trees and grasses. Switzerland is largely mountainous, and only 



312 



MOUNTAINS, PLATEAUS, AND LIFE 



about V& of its area is arable land. Only V7 of the three Alpine prov- 
inces of Austria is tillable. Less than l /6 of Japan can be cultivated 
readily. Such conditions mean a scanty food supply and a constant 
tendency toward over-population. They mean also that in many 
long-settled mountain regions the cultivable land is farmed intensively 




Fig. 
Islands. 



219. Terraces made, by Ifugao Igorots, island of Luzon, Philippine 



in small holdings. Every effort is made to maintain the fertility of 
the soil, so that it may grow good crops continuously. 

In many mountain regions, where all the level land has long been 
used, the slopes, too steep for agriculture by ordinary methods, have 
been utilized by making terraces (Fig. 219). Low walls are built one 
above another on the slopes, and the spaces behind filled in and cov- 
ered with soil. In this way, successive tiers of nearly level benches of 
land (terraces) are made. Terrace agriculture is practiced in parts of 
India, China, Italy, Germany, France, Switzerland, and other coun- 
tries. In Europe, much terraced land is used for vineyards. Choice 



FARMING IN MOUNTAINS 313 

fields with bearing vines equal in price the best irrigated fruit lands of 
western United States (p. 175). 

The crops which may be grown in mountains vary with the expo- 
sure, the altitude, the rainfall, the character of the soil, etc. In 
general, the slopes of a lofty mountain present successive climatic 
zones to which plant life, and animal and human life as well, are 
adjusted. If such a mountain is in low latitudes, its slopes may afford 




Fig. 220. Sheep grazing on a mountain side in Holy Cross National Forest, 
Colorado. (U. S. Forest Service.) 

conditions ranging from those of the tropics to those of the polar 
zones (p. 22). In the Alps, the following changes may be noted: (1) 
In suitable places on the sides of the lower valleys there are vineyards, 
olive orchards, and mulberry groves worked intensively by a relative- 
ly dense population. (2) Higher up, these are replaced by grain fields 
and pasture lands, among which there are forests of deciduous trees. 
This zone is less productive and settled less thickly than the first. 
(3) Still higher, hardy evergreen trees prevail, the proportion of useless 
land increases, only the hardiest grains are grown (up to about 5,300 
feet) in small fields by the sparse population, and most of the 
land with soil is devoted to pasturage and to the growing of hay for 
the winter feeding of the stock. (4) Above the "tree-line" (the upper 
limit of tree growth is about 7,600 feet) is a belt in which some of the 
slopes bear grass, where cows, sheep, and goats are pastured for a 



3H 



MOUNTAINS, PLATEAUS, AND LIFE 



short time in summer. (5) Finally, there is a waste of bare, rocky 
slopes and snow-fields, unoccupied by life which is useful to man. 

Stock-raising in mountains. Stock-raising is an important 
industry in many mountains, for slopes too steep or too rocky to be 
tilled, or too high for cultivated crops to ripen, may afford pasturage 
(Fig. 220). As suggested above, pasturing stock and growing feed 
for its use in winter constitute a leading industry in the higher Alps. 
More than half the productive area of Switzerland consists of pasture 




Fig. 221. Summer grazing in the High Alps. 

land and hay land. In spring, herdsmen take their cattle, goats, and 
sheep from the villages in the valleys up to the high pastures, advanc- 
ing, as the growth of the grass permits, close to the snow-line (Fig. 
221), where the grazing season may last only six or seven weeks. In 
autumn, the flocks and herds are driven back by stages to the lower 
valleys, where they are fed in stables during the long winter. Rais- 
ing enough hay and other fodder for the winter feeding is perhaps 
the most difficult part of the industry, and this requires hard labor 
during the summer. Stock-raising of one kind or another is a leading 
occupation in the mountains of Norway, Germany, central Asia, 
western South America, western United States, and elsewhere. 

In western United States great numbers of cattle and sheep feed on the grass 
of the public domain (land owned by the government). The use of much of the 
public domain is free and unrestricted. While this has had its advantages, it 



MINING IN MOUNTAINS 



3i5 



has resulted, at many times and places, in the overstocking of the range (pasture 
land), and a decrease in its capacity. Some system of regulation is likely to be 
adopted soon. Grazing in the National Forests is regulated now. 

Mining in mountains. Many mountains contain valuable ore 
deposits, and mining is one of the most distinctive of mountain indus- 
tries. The original source of most of the valuable metals appears to 
have been the igneous rocks (hardened lavas), and great intrusions 
of the latter form the central cores of many mountains. The metals 
probably were scattered widely through the igneous rocks to begin 
with, and were slowly concentrated into ores in veins, largely by 




Fig. 222. Bisbee, Arizona, a city which grew up about copper mines. 

ground- waters (p. 212). These veins are, for the most part, in or 
near the igneous rocks. Many of them have been exposed, and so made 
available to man, by erosion. The iron and copper of the Lake Supe- 
rior region occur in the rocks of old, worn-down mountains. Much 
of the gold mined in the West has come from igneous rock, and from 
the immediate surroundings of great intrusions of lava. In north- 
eastern Pennsylvania the folding of beds of rock containing layers of 
coal helped to change the latter into "hard coal" or anthracite. Much 
of the coal of this region was carried away later by erosion, but much 
was preserved in the down-folds of the mountains (Fig. 209). More 
than 80,000,000 tons of this coal are mined yearly (90,000,000 in 191 1), 
and much of it is sent throughout eastern and central United States. 
Cities have grown quickly from rude mining camps following the 
discovery of rich mineral deposits (Fig. 222). Thus in the late 
1870 's Leadville, Colorado, became a city of 15,000 people in a 



316 MOUNTAINS, PLATEAUS, AND LIFE 

few months, though in a sage-brush valley then difficult to reach, 
and at an elevation of 10,000 feet. Again, important mineral de- 
posits may help to gather a dense urban and industrial population 
about the borders of the mountains in which they occur, as in the case 
of the Pennine Mountains of north-central England, and the Erz 
(meaning ore) and Riesen ranges of Germany, where mining has been 
carried on for many years. 

Mountains as forest reserves. The slopes of many moun- 
tains have been left largely in timber because unsuited to agricul- 
ture, and various mountain ranges now support important lumber 




Fig. 223. Modern lumber mill in the Sierra Nevada Mountains, California. 
(U. S. Forest Service.) 

industries (Fig. 223). The relation of mountain forests to the flow of 
streams rising in them, and to the problems of navigation, water power, 
irrigation, and soil erosion has been noted (pp. 169, 290, 298). These 
problems, together with the need of insuring a permanent lumber sup- 
ply, have led various countries to regulate the use and cutting of moun- 
tain forests, and to provide that certain areas remain forest-covered. 

Japan has many steep volcanic mountains, whose slopes, if uncovered, would 
be eroded rapidly by the heavy rains; this helps to explain the fact that nearly 
3/5 of the country has been left in forest reserves, although the nation is in great 
need of more farm land. Among European countries, Germany, Switzerland, and 



IMPORTANCE OF MOUNTAIN FORESTS 317 

France have skillfully managed forest reserves on mountain slopes. Some of the 
Mediterranean countries show the evils which may follow the cutting away of 
mountain forests. In Dalmatia, for example, mountain slopes once forested 
consist now of bare rock, and are of little use to man. In parts of eastern and 
northeastern China the forests are gone, and one may travel hundreds of miles 
without seeing a single grove on the hill sides. Even the undergrowth has been 
destroyed, and in places all grass and other vegetation suited to the purpose are 
gathered for the cattle, or eaten by goats and sheep. 

Serious results have followed: (1) Heavy rains cause violent floods. Valleys 
usually without streams may be occupied suddenly by torrents which destroy 
bridges and buildings, ruin fields, and then disappear within a few hours. (2) In 
many places not enough water enters the ground to keep the water table sufficiently 
near the surface for the good of plants. (3) Erosion has been increased enormously 
(Fig. 80). Large lowland areas are covered with coarse waste, and much fine 
material is swept into the sea. (4) Timber is at a premium. In the western 
mountains forest destruction is less advanced, and travelers report meeting 
long lines of coolies carrying boards down to the plains, where they are worth the 
equivalent of $2 to $3 each, a value which restricts their use to special purposes, 
such as making coffins. 

Most of the National Forests of the United States (p. 298) are in the moun- 
tainous districts of the West (Fig. 207), where the greater part of the timber is 
found on the mountain slopes because the latter receive more rain than the sur- 
rounding plateaus and plains. Congress provided in 191 1 for a National Forest 
in the southern Appalachians, where the maintenance of a forest cover on many of 
the slopes is of great importance (pp. 173, 221). 

Mountains as pleasure resorts. The cool, invigorating sum- 
mer climate and beautiful scenery of many mountains lead thousands 
of lowland dwellers to visit them yearly. The mountains of New 
England, the Adirondacks, Catskills, and parts of the Alleghanies, 
contain many popular resorts. With the growth of population in 
western United States, the mountains of that section probably will 
be visited more and more. 

Most of the National Parks (Fig. 224) and National Monuments are in the 
West, and a number of them contain mountains or portions of mountains of unusual 
beauty and interest. The National Parks, of which there are 13 in continental 
United States, were created by Congress, and serve various purposes; they are 
intended especially to be " play-grounds for the American people." In 1905 the 
President was given power to set aside from the public domain as National Monu- 
ments any "historic landmarks, historic or prehistoric structures, or other objects 
of historic or scientific interest." There are now twenty-eight National Monu- 
ments, of which the Mount Olympus, Washington, and Grand Canyon, Arizona, 
monuments are largest. 

The Alps, situated in the midst of densely settled countries, 
are the most beautiful mountains in Europe, and have come to 
be perhaps the greatest summer resort in the world. Hundreds 



3i8 



MOUNTAINS, PLATEAUS, AND LIFE 



of hotels (Fig. 225) depend upon the tourist trade, and the enter- 
tainment of visitors has become almost a national industry. 

Other mountain resources and industries. Fur-bearing animals 
constitute an important resource of some mountain regions. They 
were once a resource in many others where few are left. 

From about 1807 to the middle of the century, the fur trade in the Rocky- 
Mountains of the United States was of great value. Trading posts were estab- 
lished in the mountains and along the larger rivers flowing eastward from them, 




Fig. 224. Map showing distribution of National Parks. 

at which a driving business was done. St. Louis was the great depot and outfitting 
point of the trade. The trappers and traders were the pathfinders of the West. 
The fur trade is still of some importance in the mountains of western Canada. 

We have seen that many mountain people are forced to make 
most of their own clothing, implements, utensils, etc. (p. 309). In 
addition, many of them make special articles of superior quality for 
sale. In this way they eke out a living, and find work during the 
winter months when little can be done out of doors. From wood, 
metals, wool, or other raw material at hand, they make artistic wares 
which are suited to mountain transportation, and command ready 
sale. Such are the carved wooden wares of the Swiss, and the lace 
made by some of the Italian mountaineers. 



ORIGIN AND EROSION OF PLATEAUS 319 

Many mountain streams afford much water power (pp. 248, 256, 
290) which will be used increasingly in the future. In most cases, 
however, much of the energy will be carried outside the mountains in 
the form of electricity, to be used in the lowlands. 



Plateaus 

Distribution. As stated elsewhere (p. 21), large plateaus occur 
for the most part in three classes of situations. (1) Some of them are 
between a lower plain on one side and higher mountains on the other, 




Fig. 225. A summer hotel in the High Alps. 

(2) some are between mountain ranges, and (3) some rise abruptly 
from the sea, or from narrow coastal plains. 

Origin. Plateaus are formed in various ways. (1) Some have 
been built by many lava flows, like the Columbian Plateau of the 
Northwest (Fig. 104) and the Deccan Plateau of India. (2) Adjacent 
land may have been worn low or warped down, leaving a plateau. (3) 
The plateau may have been warped or faulted above its surroundings. 

The erosion of plateaus. Like mountains, all plateaus will be 
worn down to lowlands, if not made high again. Mature plateaus 
are table-lands well dissected by streams; the surface is carved into 
hills (or mountains) and valleys (or canyons), and slope and relief 
are at a maximum. Some dissected plateaus are called mountains 
(e. g. the Catskills, p. 306). In one sense there are no old plateaus, 
for, when worn low, they are plains. 



320 



MOUNTAINS, PLATEAUS, AND LIFE 



Conditions of life on plateaus. The conditions of life on high, 
dissected plateaus are much like those in mountains situated similar- 
ly (pp. 309-318), while the conditions on many low plateaus resemble 
closely those on neighboring plains (Chapter XVIII) . Large plateaus 
in continental interiors surrounded by mountains are, in general, 
deserts, and subject to great ranges in temperature. Accordingly, 
they are settled sparsely. Farming is confined for the most part to 
the slopes of waste at the bases of rain-catching mountains, where 
water may be led from the withering streams for use in irrigation. 
The greater part of such plateaus is uninhabited, save by bands of 
wandering nomads, as in central Asia, or by occasional ranchmen 
whose cattle and sheep graze on the thin and scattered growth of 
grass, as in parts of western United States. 

The habitability of a high plateau is influenced greatly by its 
latitude; while such a plateau is cold and uninviting in the temperate 
zone, it has a temperate climate in the tropics, where, if other 
conditions are favorable, it may have a population much denser than 
that of the neighboring lowlands. 

Nearly three-fourths of the people of Bolivia live at altitudes of 6,000 to 
14,000 feet, and of the nine most thickly settled provinces, five are at elevations 
greater than 1 1 ,000 feet. Three-fourths of the population of Ecuador are found 
in the plateau basins of the Andean highlands, at an average elevation of 8,000 
feet. There is a striking contrast also between parts of the cool plateau and the hot 
lowlands of Mexico. The former have relatively dense and progressive popula- 
tions, while the latter are settled sparsely by backward Indians. In higher lati- 
tudes, plateaus for various reasons are in general settled much less densely than the 
neighboring plains, as already indicated. The Great Basin and Columbian 
Plateau of western United States each contained, in 1900, only 0.5 per cent 

of the population of the country. In 
these regions the population num- 
bered only 1.6 and 3.2 persons, respec- 
tively, per square mile. The sparsest 
population of Great Britain is found 
in the Highlands of Scotland. 




Questions 

1. (1) In what stage of erosion 

are the mountains shown in Fig. 226? 

(2) How will the slopes of these 

mountains be changed in the future? 

2. (1) What is the age, in terms of erosion, of the mountains shown in Fig. 208? 

(2) What was the topographic age of the surface from which the mountains were 

formed? The evidence? 



Fig. 226. Sketch of mountainous region. 



QUESTIONS 



321 



3. (1) Compare and contrast the climate of the mountains and plain shown 
in Fig. 227. Why the differences? (2) What work are the streams doing in the 
mountains? On the plain? Reasons in each case? (3) What kinds of soil would 
you expect to find on the plain just west of the mountains? Why? (4) What 




Fig. 227. Portion of Paradise, Nevada, topographic sheet. Scale 4 miles 
per inch. (U. S. Geol. Surv.) 



does the map suggest concerning the chances for successful agriculture in the 
different parts of the area? 

4. Compare and contrast the relations of mountains to the life of (1) primitive 
and (2) advanced peoples. 

5. Account for the fact that houses in arid plateaus often are built with flat 
roofs and thick walls. 



CHAPTER XVIII 
PLAINS AND THEIR RELATIONS TO LIFE 

Origin and classes of plains. Various types of plains have 
been discussed in previous pages, and some of their relations to 
human affairs noted. Rivers make flood-plains (p. 236), delta plains 
(p. 241), and peneplains (p. 227). The ancient ice-sheets formed 
vast drift plains or glacial plains (p. 260). The floors of extinct 
lakes form many nearly flat lake plains, especially in glaciated regions 
(p. 262). Most lake plains are small. 

Extensive plains, like the Atlantic and Gulf coastal plains of 
the United States and the vast interior plain which stretches from 
the Appalachians to the Rockies, cannot in most cases be put in 
any of the above classes. They commonly contain many smaller 
plains of several or all of the types mentioned. In general, large 
coastal plains were once marginal sea-bottoms, and were made into 
land by being raised or by the sinking of the sea. Coastal plains may 
also be peneplains, or they may be land made by the filling of a shallow 
sea border by sediment washed from the land. Large interior plains 
are either areas worn low, or, in more cases, they are former coastal 
plains now separated from the sea by newer land. The changes made 
in plains by erosion were discussed in Chapter XV. 

Distribution of extensive plains. Most of the great plains of 
the world are in the northern hemisphere. The northern parts of the 
large plains which border the Arctic Ocean are of little value to man, 
but there are vast, fertile plains in the north temperate zone which 
are of great importance in the life of the world. The southern conti- 
nents are unfortunate in having their largest lowlands within the 
tropics, where climatic conditions retard human progress. 

General advantages of plains. From the standpoint of human 
occupation, plains which possess a favorable climate have distinct 
advantages over mountains and plateaus. In general, the slopes 
of plains are gentler, their soils thicker and more fertile, and they 
have a much smaller percentage of useless land. Their advantages 

322 



PLAINS AND HUMAN PROGRESS 323 

of climate, soil, and topography make plains the great agricultural 
regions of the world. In this connection it should be remembered 
that agriculture is the basis of all lasting advance in civilization. 
Movement is relatively easy on plains, and difficult in mountains 
(p. 307). This means that goods and ideas circulate more readily, 
and that trade and culture develop more rapidly, among lowland 
people. In mountains, a great variety of conditions may be found 
within a small area, while on plains, similar conditions may prevail 
over large areas. It follows that most occupations of plains have a 
much wider distribution than those of mountains. 

Because of the advantages of lowlands for agriculture and trade, 
the great majority of the people of the world live on them. The rela- 
tively dense populations of the favored lowlands of the United States 
are shown by Fig. 281. More than °/io of the people of the country 
live on lands less than 1,500 feet above the sea. While this shows 
that most of the people live on plains, it will be remembered that there 
are plateaus and mountains lower than 1,500 feet, while a part of the 
Great Plains is much higher. Less than 1 per cent of the people live 
at elevations of more than 6,000 feet. 

Contrasts among plains. Apart from their mode of origin, plains 
differ in many ways. They may be large or small, high or low, rough 
or smooth, forested or treeless, fertile or infertile, wet or dry, and 
they may be in hot, temperate, or cold regions. Furthermore, there 
are all gradations between these extremes. These differences affect 
human interests in important ways, many of which have been noted. 

Relatively small plains protected by natural barriers, rather than large, open 
ones, favor early progress in civilization. A small area hastens advance to the 
agricultural stage (Why?), and as the population increases, laws and customs are 
made in the attempt to overcome the friction which goes with crowding. The 
isolated and protected plains of Greece possessed many advantages for early 
progress. On the other hand, all parts of a vast plain not protected by barriers, 
such as that of Russia, are open to attack. It is easy for the people of a large 
plain to scatter in search of game and other food, and the natural food supply may 
be sufficient to postpone indefinitely the development of agriculture. Extensive 
plains, such as those of central United States, afford excellent conditions for the 
further progress of a people already advanced in civilization. This is especially 
true where, as in the case cited, such plains have varied geographic conditions 
and resources in their different parts. 

Climate is the most important factor affecting the life of exten- 
sive plains, and the larger plains of the world are so distributed 
with reference to climate that the conditions of life in them may 



324 LIFE IN PLAINS 

be discussed briefly under the following headings: (i) Life in well- 
watered plains of middle latitudes. (2) Life in semi-arid plains. 
(3) Life in desert plains. (4) Life in Arctic plains. (5) Life in 
humid plains of low latitudes. The more important direct effects 
of various types of climate on life were discussed in Chapters IX, 
X, and XL 

Life in Well- Watered Plains of Middle Latitudes 

Plains in middle latitudes having plenty of rain are the seats of 
advanced civilizations, and some of them support dense populations. 
The soil is the most important resource of these plains, and agricul- 
ture the most wide-spread occupation. On the whole, they have 
less in the way of forests, minerals, and water power, than many high- 
lands have, but plains are by no means without these resources. Lum- 
bering and mining are carried on at many points, and commerce and 
manufacturing are developed highly in the thickly settled sections. 
In the complex life of these regions, the influence of geographic con- 
ditions is less apparent and less direct, but not less important, than in 
the simpler life of the grasslands and deserts. 

Differences in soil, in the form of the land, in drainage, etc., have their effect 
on the distribution and occupations of the people. The influence of variations in 
soil is especially great, and may be seen in many places. In the glaciated plains 
of northern United States, various kinds of soil may occur within the limits of a 
good-sized farm. Here the intelligent farmer is likely to devote each type of soil 
to the particular use or uses to which it is adapted. In other places, the character 
of the drift over several or many square miles is determined by the nature of the 
underlying rock, so that, for example, an area of sandy drift, over sandstone, may 
lie beside an area of limey-clay drift, over limestone. In a certain region in south 
central Wisconsin, the condition of the people in two such areas is very different. 
The area of fertile, limey-clay soil is said to have been settled by people of greater 
means, while the sandy area was occupied by poorer people not in a position to 
choose. The original difference appears to have increased. In the one case, there 
are attractive homes with modern conveniences, large barns, many windmills, 
improved roads, and many well-equipped schools; in the other, many of the build- 
ings are old and unpainted, few farms have windmills, roads are poor, and some of 
the schools are in an unsatisfactory condition. 

The influence of soil on the distribution and activities of people may be seen 
on a larger scale in various parts of the Atlantic and Gulf coastal plains. In 
Alabama, the northern part of the state is underlain by old rocks (Fig. 228). This 
part was land when the area of the coastal plain was under water. Sediment 
washed from the old land helped to make the strata of the coastal plain. East 
and west across the middle of the state there is a low, nearly level belt of rich soil, 
weathered from the limestone beneath. This is the inner part of the coastal plain. 



HUMAN RESPONSES TO SOIL CONDITIONS 325 

From its southern edge the ground rises rather abruptly some 200 feet, because 
of the outcrop of more resistant beds, and then slopes gently southward to the 
coast. The soils of this outer belt are much poorer than those of the inner lowland, 
except along the bottoms of the larger valleys, where there are deep, fertile loams. 
The history and present life of the state cannot be understood apart from these soil 
belts. The first American settlers, typical log-cabin pioneers, settled for the most 




Fig. 228. Fig. 229. 

Fig. 228. Map showing principal physiographic provinces of Alabama. 
Fig. 229. Map showing distribution of slaves by counties in Alabama (i860). 
Figures in legend indicate percentages of the total population. 

part in the rich inner lowland and along the fertile valley bottoms. Later, this 
was seen to be the section best suited to the growth of cotton, and many of the 
earlier settlers were pushed by the slave-owning planters north into the foothills 
of the mountains, or south into the sandy areas of the outer coastal plain. The 
inner lowland contained the largest number of slaves at the time of the Civil War 
(Fig. 229), and more than 3/^ of its present population are negroes. The outer 
zone of the coastal plain always has had a relatively sparse population, except along 
the larger valleys. There are still extensive pine forests where lumbering, the 
making of turpentine, and grazing are leading industries. Mobile is the only 
important city in this part of the state. It has a harbor at the drowned mouths of 
the leading rivers of the region, and is the natural gateway into the state from the 
south. 



326 LIFE IN PLAINS 

Life in Semi-Arid Plains 

Large semi-arid plains occur in the belt of the trade-winds, where 
some of them merge into deserts, as in northern Africa and Australia. 
Others lie in the interiors of continents, where the prevailing winds 
which reach them have been robbed of most of their moisture in pass- 
ing over mountains. The steppes of western Asia and the Great 
Plains of the United States are examples. The scanty rainfall of such 
plains or its unfavorable distribution prevents the growth of most 




Fig. 230. Home of native nomad of Argentine Patagonia. (Harriet Chalmers 
Adams.) 

trees except along the streams, and restricts useful vegetation to quick- 
growing grasses and a few other hardy types of plants. 

Hunting tribes and pastoral nomads. Under primitive con- 
ditions, the inhabitants of semi-arid plains get their support from 
flocks and herds, or depend on the chase, like the buffalo-hunting 
tribes of earlier years on the Great Plains (p. 328). Both the pursuit 
of game, and the frequent need for fresh pastures with new supplies 
of water, cause the people to lead a nomadic life. The dwellings must 
be such that they can be moved easily (Fig. 230); in many cases 
they are tents of skins, or of felt made from wool. Personal effects 
and household utensils are few and light; and the most desirable form 
of wealth is flocks or herds, which transport themselves. 






LIFE IN SEMI-ARID UNITED STATES 327 

The movements of many pastoral tribes are regulated by the 
seasons. In some cases, their flocks and herds are driven in summer 
into the highlands, thus escaping from the hotter plains and using 
more of the pasturage. The Kirghiz of Russian Turkestan regularly 
take their flocks in summer up into the Altai Mountains, and bring 
them back to the lower lands in winter. Again, the more abundant 
grass and water of the rainy season may permit the people to gather 
in considerable groups in desirable localities, while in the dry season 
they are forced to scatter widely, to secure food for their animals. 

The pastoral nomads of semi-arid plains always have been maraud- 
ers and conquerors, though less so than the men of the desert (p. 
333). Under favorable conditions, their growing herds and flocks 
require more and more pasture, and from time to time compel them 
to move beyond the boundaries within which they formerly had 
roamed. On the other hand a long and severe drought, resulting in less 
pasturage and a failing water supply, or disease among their animals, 
may bring them to the verge of famine, and drive them to pillage and 
conquest. Mounted on horses or camels, the nomads are able to 
make swift attacks on the people of neighboring lands, and to retreat 
quickly with their booty. For centuries, portions of agricultural 
Russia were pillaged repeatedly by hordes of horsemen from the 
southeastern steppes, and the Great Wall of China was built as a pro- 
tection against pastoral nomads. 

In general, it may be said that the conditions of life in semi- 
arid, grassy plains rarely, if ever, permit their native tribes to develop 
more than a low form of civilization. 

Use of semi-arid plains by civilized people. Even where 
civilization is advanced, plains that are too dry for agriculture by 
ordinary methods are devoted largely to the grazing industry. Vast 
semi-arid areas are used in this way in the United States, Argen- 
tina, Australia, and Russia. By means of irrigation and special 
methods of cultivation, agriculture doubtless will be extended great- 
ly in semi-arid regions in years to come. 

The Great Plains. The history of the western portion of the 
Great Plains illustrates many of the conditions of life in semi-arid 
regions. Until after the Civil War, these plains were occupied by 
Indians dependent for a living on the great herds of buffaloes. The 
killing of the buffalo and the confining of the Indians to certain areas 
(reservations) opened the plains to the cattle industry. In the drier 
parts most attempts to farm by ordinary methods have been un- 



328 LIFE IN PLAINS 

successful, though here and there streams and wells furnish water for 
irrigation (p. 329). Within the last few years, "dry farming" 
(p. 329) has replaced the grazing industry in some places. 

As already indicated, the buffalo was the most important factor in the lives of 
many Indians of the Great Plains. The chase required many quick moves, and 
this helped to keep families rather small, the houses light and portable, and personal 
property small in amount. Individual ownership of land was unknown among 
some of the tribes. The mythology of the Indians was tinged by their hunting 
and military habits. The chiefs attained their positions because of their skill as 
hunters or warriors. With the disappearance of the buffaloes, the hunting tribes 
lost their chief support, and became dependent on the white man. Great numbers 
of buffaloes were killed as food for the construction gangs of western railroads, 
and for their hides, which were in great demand in the East for robes, belting for 
machinery, and other purposes. They practically disappeared from the southern 
plains in the middle seventies, and from the northern plains a few years later. 

The stock-raising industry of the Great Plains began in Texas and spread north- 
ward. Cattle were introduced into Mexico by the Spaniards about 1525, and before 
the Revolutionary War there were large cattle ranches north of the Rio Grande. 
In the middle 1850's, most of Texas was "a vast, unfenced feeding ground for 
cattle, horses, and sheep." At the close of the Civil War, cattle were very cheap 
in Texas, but brought high prices and were in great demand in the northern cities. 
As a result, the practice was developed of driving cattle northward in great herds 
to shipping points on the railroads that were then building across the Great Plains 
in Kansas and Nebraska. The "cow towns," as the shipping points were called, 
were established beyond the farming frontier, preferably where there was a good 
supply of water and grass. The business shifted west and south with the advancing 
railroads, keeping in front of the farming zone. The banner year of the Texas 
cattle drive was 1884, when 1,000,000 cattle were driven out of the state. Soon 
after, the drives were rendered unnecessary by the extension of railroads, which 
took the stock to market in much less time and usually in better condition. The 
stocking of the northern lands occurred, for the most part, after 1870, and before 
the close of another decade the business had spread to the Canadian boundary. 
For a time, large returns were realized from feeding cattle on the public grass. 
Many people accordingly went into the business, and in numerous places the range 
(unfenced pasture land) was overstocked and the pasturage injured. One result 
of this in many places was the introduction of sheep, which can live on pasturage 
that will not support cattle. The conflicting interests of cattlemen and sheepmen 
have caused much trouble in some of the grazing states. The development of the 
grazing industry on the Great Plains had an important influence upon the growth 
of the slaughtering and meat-packing industry in Kansas City, Omaha, St. Louis, 
Chicago, and (later) South Omaha, from which meat products were sent to the 
urban and industrial centers of the northeastern states and Europe. 

In 1880, the Great Plains west of the 98th or 99th meridian were occupied only 
by stockmen, except along some of the larger valleys (Fig. 231). A few years later 
thousands of farmers moved there and began to grow wheat, using the seed and 
methods which they had employed farther east, where the rainfall is greater. The 
population of Kansas increased 250,000 between 1885 and 1888, largely in the 






FUTURE USE OF SEMI-ARID LANDS 



3 2 9 



IZDUnder2persq.Tni\ 

EH 2 to 6 » 

6 tola " 
18 and over 



western portion (Fig. 232). The agricultural invasion began because of heavy rains 
in the middle eighties, and was kept up for a few years by the advertising of railroads 
and the activity of town-builders and land-dealers. Then came several very dry 
years, and thousands were starved out of the region. Kansas lost some 200,000 
people, and the western 
parts of Nebraska, the Da- 
kotas, and the eastern part 
of Colorado were affected 
similarly (Fig. 233). Mil- 
lions of acres returned 
slowly to grass, and within 
a few years hundreds of 
"cities" were abandoned 
by their founders. Within 
the last few years, another 
agricultural invasion of the 
High Plains has been in 
progress. A series of wet 
seasons, the activity of land 
companies, and the intro- 
duction of agricultural me- 
thods adapted to semi-arid 
conditions have been the 
le*ading causes. The out- 
come is still uncertain, but 
is not likely to be so disas- 
trous as the first settlement, 
because men know better 
now how to make use of 
dry lands. 

The chief uses to which 
the semi-arid parts of the 
Great Plains will probably 
be put in the future may 
be suggested briefly. (1) 
Farming by irrigation will 
be extended somewhat, but 
the amount of water avail- 
able from all sources is but 

a small fraction of what would be needed to irrigate all the land. (2) Dry-farming, 
especially with hardy, drought-resisting plants (p. 173), promises much more than 
irrigation for the region as a whole. Dry-farming scarcely can be said to have 
passed the experimental stage, and how large an area can be dry-farmed success- 
fully is quite uncertain. As already pointed out (p. 65), dry-farming seeks (a) 
to get the largest possible amount of the rainfall to enter the ground, and (b) to 
reduce to a minimum the loss of water by evaporation from the soil. (3) Stock-rais- 
ing, and stock-raising with subordinate farming, apparently must remain the 
leading industries over large areas. 




Fig. 231. 



Fig. 232. Fig. 233. 

Figs. 231, 232, 233. Maps showing distribution 
of population on the western Great Plains in 1880, 
1890, and 1900. 



33 o LIFE IN PLAINS 

Life in Arid Plains 

About Vs of the land is desert for lack of rain. By no means all 
dry deserts are plains; some are plateaus, and within desert plains and 
desert plateaus there may be ranges of high hills and mountains 
(p. 334), though these, in most cases, receive more rain than their sur- 
roundings. Many of the conditions of life are similar in arid plains 
and plateaus, and they are considered together. Life in cold deserts, 
such as parts of the Arctic plains (p. 336), differs greatly from that 
in dry deserts. Only the latter are considered here. 

The great deserts of the world are in the zones of the trade-winds, 
or to leeward of high mountains. Their wide distribution and vast 
extent, the location of some of them near well-watered and thickly- 
settled regions, and the relations of their people to their neighbors, 
always have given deserts great importance in the life of the world. 
Except in the relatively small areas where irrigation is possible, or to 
which people may be attracted by valuable mineral deposits, deserts 
are doomed to have scanty populations. 

The power of mineral deposits to bring people to deserts is illustrated strikingly 
in Nevada. The deposits of gold and silver first discovered there attracted thou- 
sands of miners and prospectors, and made Nevada a state in five years. Later, 
the population of the state declined greatly (p. 311), but in the last decade it has 
increased again (81.000 in 19 10) due to new discoveries of ore. Butte, Montana, 
a city of 39,000 inhabitants, is supported largely by deposits of copper that underlie 
less than two square miles of arid land which, without the mines, could support 
only a few people. 

Plant life in deserts. Plants require water for growth, and 
they lose water chiefly by evaporation from their leaves. It is clear 
that plants with unusual ability to get and store water, and plants 
which lose but little water, are best suited to deserts. Most desert 
plants are provided with many long roots, which enable them to get 
more moisture from the dry soil than would be possible otherwise, 
and at the same time help them to stand against the winds, often of 
great strength. The loss of water from the plant is reduced by such 
things as thick skins, corky bark, and coats of hair. Some desert 
plants have no leaves, and some have only a few small, rounded, and 
fleshy leaves. Thus the loss of water by evaporation is diminished. 
Many desert plants have thorns, spines, and unpleasant or poisonous 
juices, which help to protect them against devouring animals. Scat- 
tered shrubs and coarse grasses are among the leading types of desert 



THE ANIMALS OF DESERTS 331 

vegetation. Fig. 234 shows desert plants of various kinds. The 
plants of deserts have little economic value at the present time. The 
vegetation of oases (p. 334) is. quite unlike that of the desert. 

After rain falls in the desert, many small, quick-growing plants spring up, 
some of which bear bright flowers; but soon they wither and die for lack of sufficient 
water. 

Animal life in deserts. Like certain plants, some animals have 
developed characteristics which help them to live in the desert. 
The severity of desert conditions is shown, however, by the smal-1 




Fig. 234. View in the desert near Tucson, Arizona. (W. L. Tower.) 

number and the small variety of animals which can endure them. 
Like desert plants, desert animals are, as a rule, scattered. Some 
are very fleet of foot, and thus are able to move between widely 
separated watering places and to escape from their enemies. Some 
are slow-moving, but most of these are venomous, and all of them 
are able to go without water for long periods. A desert is an im- 
passable barrier to slow-moving animals which need water frequently. 
On account of the hot days and cool nights, many desert animals 
are more active during the night than during the day. Many of 
them are dull of color, and not easily seen against the barren ground. 

The camel is the most important animal of the arid regions of the Old World, 
having long been called "the ship of the desert." It is found in northern Africa 
and in Asia (Fig. 235), from Arabia to China, and northward to northern Mon- 
golia. A draft camel carries 300 to 600 pounds, according to size, the customary 
load being about )/$ the weight of the animal. It is said that caravans sometimes 
travel 20 out of the 24 hours at a steady gait of 2>£ to 3 miles an hour, halting 
only during the hottest part of the day. 



332 



LIFE IN PLAINS 



The camel is well suited to desert conditions. It can travel far with a small 
supply of food and water; it has small nostrils, which can be closed so as to prevent 
the entrance of the finest wind-driven sand; eyes protected against sand and sun by 
long, heavy lashes; and peculiar padded feet, fitted for the hot sands. The parts 
of the body exposed most to heat and friction are protected by great callosities. 
When at rest in an oasis, a camel drinks only enough for the time being, but when 
on the march it makes provision for many hours in advance. During weeks of rest 
or light work, the hump increases in size; on long journeys, the material of the 
hump is absorbed into the system, keeping up the strength of the animal. 

Human responses to desert conditions. Agriculture is impos- 
sible in deserts, without irrigation, and few places have enough 
water for that. Furthermore, grazing in many cases is possible only- 




Fig. 235. Camels in northwestern India. A portion of a caravan which has 
come through Khyber Pass from Afganistan. 

along the margins of the desert, or in oases. Since deserts afford 
little food, they can support few people, scattered widely in small 
groups. The conditions in deserts permit native tribes to make little 
progress in civilization. 

Along the borders of many deserts the conditions of life are a 
continuation of those in semi-arid grasslands (p. 326). The people 
wander from place to place with their flocks and herds, the size of 
the social group being determined by the supply of water and grass. 
Along the margins of certain deserts, the people sometimes do a 
little farming when the water supply permits, to add to the often 
uncertain and always restricted living afforded by their animals. 

We have seen (p. 331) that deserts may support considerable vegetation for a 
short time after rain falls. Along the edges of certain deserts, pasturage is available 
in the wet season, even where the surface is bare in the dry season. This may 



THE MEN OF THE DESERT 333 

control the seasonal migrations of pastoral tribes. In winter, the Arabs find scant 
pasturage for their goats and sheep on the northern border of the Sahara; in 
summer, they drive them to the slopes of the Atlas Mountains. In the same way 
flocks and herds are driven at various points into the southern edge of the Sahara 
in summer, which is there the rainy season. 

The arts of desert people are primitive and confined largely to 
household industries. Making leather and leather utensils from the 
skins of animals, pottery from clay, and blankets and rugs from wool 
furnished by the flocks, are typical industries. 

Among American Indians, the potter's art was developed best in the arid 
Southwest. Here water was scarce, and durable, water-tight vessels were an 
absolute necessity. The Navajo Indians of this region possess large flocks of 
sheep, and sell wool and blankets. The latter are made by the women in many 
artistic designs, and enjoy a wide reputation. 

From force of necessity, most wandering desert tribes are rob- 
bers. They pillage caravans and hold travelers for ransom, or exact 
heavy tolls in return for safe passage through the desert. They raid 
adjacent agricultural lands, and in some cases have levied regular 
tribute upon them, or have conquered and settled in them. The 
Sudan and Egypt have been invaded repeatedly by tribes from the 
Sahara. 

The people of deserts are excluded more or less completely from 
the culture of the outside world. Hence, as in mountains (p. 309), 
old manners and customs persist. Customs of the time of Christ 
still are observed in the desert of Arabia. Scattered widely in small 
groups, desert people develop many dialects. They are compelled 
to eat very sparingly of the few things available. Nothing is wasted; 
the Tibbus of the Sahara eat even the skins and powdered bones of 
their dead animals. The scanty diet and severe hardships incident 
to life in the desert help to produce a distinct physical type. The men 
are commonly thin, but wiry, and capable of great exertion. Desert 
nomads have great powers of observation and a remarkable sense of 
locality. Intellectual activity necessarily is restricted in the desert. 
The dull scenery and the lonely life tend to lead the mind into reverie 
and contemplation. The majesty of the larger deserts, their vast 
extent, their great dust and sand storms, and the uncertain position 
of man, all tend to inspire feelings of awe and reverence. It is sig- 
nificant that Christianity and Mohammedanism were associated close- 
ly in their origin and development with the arid and semi-arid regions 
of the Old World. 



334 LIFE IN PLAINS 

Life in oases. In deserts, permanent settlements based on 
agriculture are possible only in oases, where there is water supplied 
by springs, artesian wells, or rivers. The source of the water supply 
may be outside the desert in well-watered regions, or within the 
desert where elevations rise high enough to compel the passing 
winds to give up a part of their moisture. 

The Nejd Plateau, in the heart of Arabia, rises to an elevation of more than 
5,000 feet, and here there are fertile oases, cultivated for centuries, and extensive 
pastures. Even in the Sahara, there are a few mountains which receive enough 
rain to support trees. The streams formed on these mountain slopes disappear 
after descending to the desert. Some of the narrow valleys are farmed, and grazing 
is possible over larger areas. 

Some oases serve merely as headquarters for tribes which roam 
over the surrounding desert in search of pasturage, and of caravans 
which they may attack. Some support towns, most of which are 
small. In general, the larger towns are located on the main caravan 
routes, where there is better opportunity for trade (p. 335). The 
houses in many cases are built of stone or adobe (sun-dried clay). 
In many cases, oases are cultivated most carefully in order to secure 
the largest possible returns from the restricted area which can be 
watered. Vegetables, cereals, and fruits, especially dates, are grown 
in the oases of the Sahara and the deserts of southwestern Asia. 

The date palm has a trunk in some cases fifty to sixty feet high, ending in a 
great crown of feathery leaves (Fig. 236). Bearing trees average from 100 to 200 
pounds of dates a year, though yields of 500 or 600 pounds have been known. 
A tree may bear fruit for a century. The date palm is adjusted perfectly to 
conditions in the oases of low-latitude deserts, for it requires a dry, hot climate, 
and a moist soil. It has been said with truth that the Arabs built their lives on the 
date palm. In the future, the date palm probably will have commercial value in 
irrigated lands along the lower Colorado River (p. 242) and about Phoenix, Arizona. 

Oases in deserts are in striking contrast with the barren land 
about them, though most of them are not such delightful gardens as 
they have been described. They are subject to frequent sand-storms, 
their water supply is small and in many cases impure, and their prod- 
ucts are restricted in variety and in quantity. 

Commerce of the desert. Where a desert lies between well- 
watered and populous regions, important trade may be carried on 
across it. Some trade is carried on also between agricultural lands 
and the borders of neighboring deserts, because of their contrasted 
resources and the desire of the desert people to supplement their 



TRADE IN THE DESERT 



335 



meager products. Timbuctoo, on the Niger River, and Damascus, 
in Syria, are examples of places which serve as gateways to deserts. 

For centuries, goods were carried in large quantities across the vast deserts of 
central and western Asia only by pack animals, especially the camel, and even to- 
day this is the case over much of the region (Fig. 235). A number of caravan 
routes cross the Sahara, ex- 
tending from oasis to oasis. 
The trade which originates 
or terminates in the Sahara 
is largely in dates, salt, 
clothing, cereals, and camels, 
while for centuries the 
through trade has included 
such things as ivory., gums, 
spices, and gold dust. 
Prince Henry of Portugal 
learned of the trans-Saharan 
trade while on an expedition 
against the Moors in north- 
ern Africa in 1415, and 
partly with the idea of 
diverting the trade of the 
Guinea Coast to his own 
country by water, he began 
the long series of explora- 
tions along the coast of 
Africa which culminated in 
the discovery of the all- 
water route to India. The 
use of the latter route to the 
East injured greatly the 
caravan trade across Asia. 
A trans-Saharan railroad is 
now projected. 

Political conditions 
in deserts. The hard 
conditions of life in 
deserts repeatedly have 
driven their inhabitants 
out to conquer other regions (p. 333). On the other hand, the con- 
quest of deserts from without always has been attended by great 
difficulties, and in some cases never has been accomplished. The 
love of freedom and the fighting ability characteristic of desert 
peoples, in addition to the difficulties which an invading army finds 
in the lack of roads, water, and food, have helped to produce this 



# 




•'■'• 






**1 








.,**=•-•«'■■•.? 


'• ^gg^3r*' *^W^^' \,l 


^TIP* -* 




1 



Fig. 236. Date 
Biskra, Algeria. 



palms loaded with fruit. 



33^ 



LIFE IN PLAINS 



result. Furthermore, the scant resources of deserts have made 
them relatively uninviting to outside people. 



Life in Arctic Plains 

The plains which border the Arctic Ocean are known as barren 
lands in North America, and as tundras in Eurasia. They are cold 
deserts, snow-covered for some two-thirds of the year. The short sum- 
mers, low temperatures, and cold or frozen soil prevent agriculture, 
and restrict vegetation chiefly to stunted bushes, mosses, and various 
quick-growing, flowering plants. The few, widely scattered inhabit- 
ants of the tundras depend largely on their herds of reindeer and on 




Fig. 237. Reindeer and sledge. 



hunting for their living. Fishing is an important occupation during 
the three or four months when the streams are free from ice. A 
nomadic life results from the necessity of following the game and 
the reindeer herds, which wander half-free in search of pasturage. 
As in the steppes and dry deserts, this nomadic life means small, 
easily transported dwellings — in many cases a tent consisting of a 
framework of poles covered with skins — and few and simple house- 
hold goods. Some of the tribes move northward with their herds 
in the summer, and return to pass the winter in the forests which 
border the tundras on the south. Here the timber affords some 
shelter, feed is available for the reindeer, and game may be hunted 
for food and fur. 



THE NATIVES OF TROPICAL FORESTS 337 

All that the camel is to the inhabitants of low-latitude deserts, the reindeer is 
to the men of the Arctic desert. It is indifferent to cold, and is an excellent draft 
animal (Fig. 237). Its milk and flesh are used for food; its bones and horns afford 
material for making various implements ; its tendons and sinews serve for thread; and 
its skin is used for shelter and clothing. The reindeer is the most desirable form 
of wealth on the tundra. In some places, a herd of 50 head, which will support 
a family of four or five, requires between 4 and 5 square miles of tundra pasturage. 
This means at best a very sparse population. 

Some years ago the United States Government imported nearly 1,300 reindeer 
from Siberia, for the benefit of the natives of northern Alaska. The herds have 
increased rapidly, and are proving of great value. 

In the Arctic plains life is a constant struggle for food, clothing, 
and shelter. There is little opportunity for trade. Situated on the 
outskirts of the inhabited world, the frozen deserts of the north have 
played a much less important part in history than the centrally- 
located deserts of lower latitudes. Nor does it seem likely that they 
can become of much importance in the future. 

Life in Humid Plains of Low Latitudes 

Near the equator, the climate of the lowlands is characterized 
by heavy and frequent rains, and by high, nearly uniform tempera- 
tures throughout the year (p. 102). As we have seen, this results 
in a dense, varied vegetation (Fig. 238), like the forests of the Amazon 
and Congo valleys. The distinctive life of humid plains in low lati- 
tudes is therefore that of the tropical forest, or jungle. In some of the 
other realms which we have considered, man has been handicapped 
by lack of useful vegetation. Here, the very abundance of plant life 
is an obstacle to progress. 

Response of natives to conditions in tropical forests. The 
dense forests of equatorial regions are occupied by sparse populations 
of backward natives. The high temperatures and the moisture are 
enervating, and steady work is difficult. The luxuriance of the 
natural vegetation makes the clearing of land difficult, and after it 
is cleared, a constant struggle is necessary to keep out the plants which 
are not wanted. Unused trails through the forest are overgrown 
quickly, and all trace of settlement soon disappears from abandoned 
clearings. Under these conditions, it is not strange that agriculture 
rarely is practiced. Throughout the world, man appears, as a rule, 
to have developed agriculture, or to have domesticated animals, 
only when the natural food supply became too small. In the equa- 
torial forest, the natural food supply is abundant. The natives live 



338 



LIFE IN PLAINS 



chiefly on the fish afforded by the many rivers, and such game as 
inhabits the forest. This is supplemented in many places by the 
products of certain forest plants, such as the sago palm. 

The large animals found in many places in the open country near the tropical 
forests go into the latter only a short distance. They come and go through the 
denser growth by paths which they keep open by frequent passing. In the heart 
of the forest, there are few sources of food for animals near the ground. Flowers 
and fruits are found in the tree tops, however, and hence animal life is represented 




Fig. 238. 
Tower.) 



Tropical forest and river in flood. Southern Mexico. (W. L. 



chiefly by flying and climbing forms, such as insects, birds, snakes, and monkeys. 
Many of the birds and snakes resemble the foliage in color, a fact which favors 
concealment. 

Little is needed by the inhabitants of the tropical forest in the 
way of clothing and shelter. Some of the lowest savages have no 
homes. Some of the people live in floating houses on the rivers, or 
in huts built on piles to escape the floods. Rivers are the most im- 
portant lines of travel through the forest. 

A little farming is done in clearings near the edges of the equatorial 
forests. In some cases, this consists in scarcely more than planting 



PYGMIES OF THE CONGO FOREST 



339 



crops, and leaving them to grow. Bananas, bread fruit, rice, and other 
things are grown in different places, chiefly by the women. Very 
little labor brings large returns, so that steady effort is discouraged. 
As in the equatorial forest generally, life is too easy; there is no spur 
to progress. 

The Pygmies who live in parts of the Congo forest are perhaps the lowest type 
of human beings. Most of the adults are only a little more than 4 feet tall, and 
many are shorter. They make no attempt at farming, but live by hunting and 
fishing. They kill small game with arrows and spears tipped with a poison made 
from certain plants, and capture even large animals in covered pitfalls which they 




Fig. 239. Pygmy village in the Congo forest. 



make in the narrow runways followed by the animals (p. 338). They catch fish 
in nets or baskets. They live in small, scattered groups where there are openings 
in the undergrowth (Fig. 239), building temporary huts consisting in many cases of 
flexible sticks covered with leaves, and shifting from spot to spot in quest of game. 
They carry on some trade with other tribes, bartering meat, skins, and plant 
poisons, for weapons and vegetable food. The Pygmies have no arts save those 
connected with their hunting and fishing, and no family ties. 

Commerce of tropical forests. The forests of tropical low- 
lands furnish products of much importance to the outside world, 
such as ebony, mahogany, rubber, gums, palm-oil, and copra. Trade 
follows the waterways, and in general those sections are most favored 
commercially which are situated conveniently with reference to a 
navigable river (p. 104). 



34Q LIFE IN PLAINS 

The humid lowlands of the tropics are of far greater importance 
to man than the Arctic plains, but unfortunately the settlement and 
development of them by people from middle latitudes are attended 
with great difficulty (pp. ioo, 103-104). 



Questions 

1. How might one prove that a given coastal plain was formerly a marginal 
sea-bottom? 

2. By what are the characteristics (topography, fertility, etc.) of any given 
plain determined? 

3. Why are the soils of most plains thicker and more fertile than those of 
plateaus and mountains? 

4. (1) What great plains, now of little value to man, are likely to have greatly 
increased importance in the future? Why? (2) What ones are likely to continue 
of little significance? Why? 

5. Compare and contrast the life of primitive peoples in arid deserts and rugged 
mountains. 

6. How does the life of people in Arctic regions resemble that of desert tribes 
in lower latitudes? 



CHAPTER XIX 
COAST-LINES AND HARBORS 

Importance of coast-lines. There is great freedom of move- 
ment over the ocean. A ship may sail direct from one port to another 
thousands of miles away, or it may make a roundabout voyage, call- 
ing at many ports on the way. A modern steamship can carry ten 
to twenty train loads of freight in a single cargo, and it costs far less 
to operate one steamer than to run ten or twenty trains. Furthermore, 
trains call for the maintenance of a railway, which is very expensive. 
Hence the carriage of freight by rail is much more costly than by boat. 
Modern commerce, therefore, depends much on the ocean highway, 
but it owes its rapid growth in part to favorable coast-lines through 
which access to the sea is secured. 

In early days, seamanship was much influenced by the character 
of the coast-line. It was unsafe to go far from land, for vessels were 
small and there was no way of determining position accurately, or 
of reckoning distances. Hence seamanship developed first along 
the shores of quiet inland seas like the Mediterranean, or where long 
bays and sheltering islands invited ventures from one headland or 
island to another, as in Norway. Thus the first nations to become 
sailors, fishermen, explorers, and sea traders were influenced by the 
nature of their sea-coasts. 

With modern steamships and skillful seamen, voyages are under- 
taken readily to distant parts of the earth. But even the giant steam- 
ship needs safe anchorage in quiet waters while its cargo is being load- 
ed or unloaded. Some ocean commerce is carried on from places 
which have no harbor, but in such cases, vessels anchor off shore while 
the cargo is carried {lightered) from them to shore, or from shore to 
them, in small boats. During heavy seas lightering is impossible, 
and many wares cannot be handled to advantage in this way at any 
time. 

Characteristics of coast-lines and their origin. If land along 
a coast were to be elevated or the sea-level lowered, a portion of 

34i 



342 



COAST-LINES AND HARBORS 



the sea floor would be exposed. Most of the sea floor is smooth 
and even. Hence the emergence of a coastal strip tends to make 
an even, regular shore-line (Fig. 240) fronted by shallow water. 
Coasts which have risen recently, relative to sea-level, are without 
good harbors, except where some large river, flowing across the 
coastal plain, offers a haven at its mouth. Commerce with such a 
coast is at a disadvantage. Large vessels must anchor off shore while 
their cargoes are lightered, unless artificial harbors have been made by 




Fig. 240. Map showing regular outline of a newly elevated coast. Dotted 
lines indicate contours; interval 25 feet. (Nome, Alaska, Special Sheet, U. S. 
Geol. Surv.) 



building breakwaters, jetties, or long quays. The east coast of 
India and most of the Gulf coast of Mexico present these conditions. 
Madras and Vera Cruz have artificial harbors because the trade from 
an important region justified the great expense involved in making 
a harbor. 

The submergence of a coast land having hills and valleys pro- 
duces a new shore-line which is irregular, the drowned valleys form- 
ing bays (Fig. 241). Isolated hills on the old lowlands may front the 
new coast as islands. The coast of Maine furnishes good examples. 
Such a coast-line commonly has many sheltered bays and harbors. 
Commerce is favored by such a coast. Most important commercial 
ports, such as the Atlantic ports of North America and Europe, are 
along depressed coasts. The chief sea fisheries, also, are connected 
with irregular coasts, partly because of the many convenient refuges 



EMBAYED COAST-LINES 



343 



for fishing fleets. Not infrequently, also, large bays, like Chesapeake 
Bay, support valuable fisheries. 

Where an irregular coast-line is produced by the sinking of a coastal plain, 
the bays may be wide (Why?), like Delaware and Chesapeake bays, but most of 
them are shallow, except along the line of the old river channel, and they may have 
marshy land along their borders. Few places on the shores of such bays are 
suitable for the development of a great port. Where a higher, more rugged region 




Fig. 241. Map showing irregular outline of a depressed coast. Dotted lines 
indicate contours; interval 20 feet. (Monhegan, Maine, Sheet, U. S. Geol. Surv.) 



is submerged, the bays are likely to be narrow and fiord-like, as in Alaska and 
Norway. Most of them are deep, and some are bordered by high land which rises 
so abruptly from the water that there is no room for a city. 

Where the ocean finds access to an interior valley, a long inland arm of the sea, 
like Puget Sound, is developed. A former mountain pass in the Coast Range, now 
submerged, forms the picturesque Golden Gate entrance to San Francisco harbor 
(Fig. 242) , and a little further sinking would change much of the central valley of 
California into a great sound. 

Changes in shore-lines. Shore-lines are subject to constant 
change by waves, shore and tidal currents, rivers, winds, and ice. 



344 



COAST-LINES AND HARBORS 



The effect of glaciers on shore-lines has been noted (pp. 256, 261). 
Much of the value of Boston harbor depends on the protection 
afforded by islands of glacial origin. Shore ice has little effect on 
coast-lines, but hinders navigation along some coasts (p. 246). 

Winds often make dunes on the sea shore (p. 202), and the dunes 
may afford the land some protection from the sea, as along the coast 




Fig. 242. Diagram showing arm of ocean formed by invasion of valley through 
a submerged sag in mountain range. San Francisco harbor. Dotted lines indi- 
cate bar across entrance. (U. S. Coast and Geod. Surv., Chart No. 5500.) 



of Holland, but they rarely change the outline of the land to any 
great extent. 

Rivers affect shore-lines little by erosion, but delta-building 
rivers may change them greatly (p. 241). Other things equal, delta 
lands grow most rapidly in the quiet waters of bays and inland seas. 
Thus the delta of the Mississippi (Fig. 159) extends into the Gulf as 
a great irregularity, with many smaller irregularities about its borders. 
Delta-building in bays may lessen the irregularities of the coast by 
filling the bays. The value of Mobile Bay as a harbor is lessened 
because of the sediment deposited in it, and many others, which were 
important ports centuries ago, are now partly or entirely filled. The 



WAVES AND SHORE CURRENTS 



345 



city of Adria, Italy, once the port for the mouth of the Po, is now 
fourteen miles from the coast, and the Rhone delta, building forward 
at the rate of 200 feet a year, has never developed an important port 
(p. 270). 

On exposed coasts, delta-building is less rapid (Why?), and pro- 
duces fewer irregularities. The delta of the Amazon, for example, 
does not project be- 
yond the general coast- 
line. Delta lands are 
low, marshy, and sub- 
ject to floods, while 
the bays about their 
borders are shallow. 
For these reasons del- 
tas are poorly suited to 
the development of 
ports, and except at the 
mouths of great rivers, 
like the Mississippi, 
deltas rarely become 
the sites of great com- 
mercial cities. 

Waves are the chief 
agent changing coast- 
lines. On irregular 
coasts, the general tend- 
ency of waves is to wear away headlands (Fig. 243) and fill bays, 
thus making the shore more regular. On regular coasts, their gen- 
eral tendency is to wear back the shore-line. Waves therefore tend 
to destroy harbors. In many cases serious harm to commerce is 
prevented only by costly structures built to protect and improve 
harbors. 

Waves are at work almost constantly on some part of every 
coast-line. Large waves are more powerful than small ones; hence 
coasts exposed to stormy seas are worn most, and those of loose 
material, such as gravel and sand, are cut back more than those of 
solid rock. The gravel, sand, and clay of the Atlantic Coastal Plain, 
and the glacial drift of parts of New England, are washed away more 
readily than the solid rocks of Maine or Norway. 

In deep water away from shore, the water in a wave does not move 









4*£ 




m 








S§i 






■ 









Fig. 243. Wave erosion of an exposed headland. 



346 



COAST- LINES AND HARBORS 



forward. An idea of its motion may be gained from a field of waving 
grain, where wave after wave crosses the field, though each moving 
stem is fixed to the ground. But when a wave advances into shallow 
water, its motion changes because the lower part of the wave drags 
bottom, and so is made to go more slowly. The top tends to pitch 
forward, making surf (Fig. 244). A somewhat similar effect may be 
produced in deep water when winds blow the tops of waves forward, 
forming whitecaps. Hence during storms, and especially in shallow 




Fig. 244. Surf wave at Point Buchon, California. 



water, there may be a distinct forward movement of the water in a 
wave, but generally in deep water it is only the wave motion, not 
the water, which travels forward. 

In shallow water, the water which is thrown forward against 
the shore runs back down the slope of the bottom as the undertow. 
Drownings have resulted so frequently from bathers being caught by 
the undertow that many bathing beaches now have regular life guards 
constantly on watch during bathing hours. 

If waves reach the shore obliquely, they produce a movement 
of water parallel to it. Such a movement is known as a shore or 
littoral current. Where a shore is exposed to winds prevailingly from 
one quarter, the resulting shore currents are somewhat constant 
in direction. Littoral currents are most important in moving the 
material worn from the land by waves. 



CLIFFS AND TERRACES 



347 




Fig. 245. A cliff fronted by a terrace. 
Outer (dotted) part of terrace built by- 
deposition of sediment; inner part due 
to wave cutting. 



Erosion by waves. The force of waves hurled against the 
shore may be very great. Surf has been thrown to heights of more 
than 100 feet with force enough to destroy lighthouses. The strength 
of waves on the coast of Great Britain is sometimes as much as 
three tons per square foot. Such waves are able to move masses 
of rock weighing several tons. 
During one storm more than 
200 blocks of concrete, weighing 
4 tons each, were swept, from 
the break-water at Cherbourg, 
France, and tossed over an em- 
bankment. It is clear, there- 
fore, that the force of waves is 
great enough to wear shores, 
even of solid rock. Where deep 
water is found near shore, as 
along most steep coasts, erosion depends on the work of the water 
alone. Where waves break in shallow water, pieces of rock may be 
hurled forward with the rushing water, and serve as powerful tools to 
cut away the land. In severe storms, the land is, in rare cases, driven 
back many feet in a few hours. The waves of lakes are never so strong 
as the great waves of the sea (Why?), but the storm waves of large lakes 
have great force, and may do much damage even in a single storm. 

The great force of waves on an exposed coast has led to many 
attempts in different countries to use wave power for industrial 
purposes. None of the 
devices yet tried has 
proved practicable on 
an important scale. 
One obstacle is the ex- 
tremely variable char- 
acter of the waves. 

Where waves erode 
the land they make 
steep slopes, or cliffs. 
Such cliffs are bordered 

by wave-cut terraces a little below the surface of the water (Fig. 245). 
The width of such a terrace measures roughly the advance of the 
water on the land by the cutting of its waves. By rise of the land, 
or by sinking of the sea, the terrace may become land (Fig. 246). 




Fig. 246. Wave-cut terraces now well above 
the sea, indicating relative change in level of land 
and sea. Seward Peninsula, Alaska. 



348 



COAST-LINES AND HARBORS 




By driving back sea cliffs, waves tend to increase the area of the sea 
at the expense of the land. The island of Heligoland, off the German 
coast, has been so worn by waves that it is less than one-twentieth 
as large as it was a thousand years ago. Many shoal areas off the 

New England coast are 
due to the cutting 
away of small islands. 
Deposition by 
waves and shore cur- 
rents. Material worn 
from the land by waves, 
or brought to the shore 
by rivers, is shifted 
about by waves, under- 
tow, and shore cur- 
rents, but finally comes 
to rest. If left at the 
shore-line it makes a 
beach (Fig. 247). If 
carried farther out into 
the water, it takes on 
other forms. Fine par- 
ticles of mud generally are carried out into deeper water, while 
coarser material, such as sand and gravel, make the beach. 

Waves may build reefs or barriers a little way out from the shore. 
They are formed near the line of breakers, where the incoming wave 
leaves much of the sediment which it is moving toward the land. 
The undertow may add to the reef by carrying sediment out from 
the shore. Some reefs are troublesome to navigation, especially 

where they make "a bar" at 
the entrance to a harbor. 

Waves may build the crest 
of a reef above water, convert- 
ing it into land (Fig. 248). By 
building dunes, the wind may 
then aid in raising the surface still higher. This seems to have 
been the origin of many low, narrow belts of sandy land parallel 
to coasts, with marshes and lagoons behind them. Such barriers 
are common in shallow water, as at many places from New York to 
Texas. Lagoons behind reefs provide harbors in some places, 



Fig. 247. Wave-cut cliff with some of the mate- 
rial left in the form of a beach at its base. Lake 
Michigan. 



Fig. 248. Diagram representing 
cross-section of a barrier beach. 



REEFS, SPITS, AND BARS 



349 



Where a shore current reaches a bay, it does not, as a rule, follow 
the outline of the bay, but tends to cross it in the direction in which 
it had been moving. Un- 
der such circumstances it 
may build an embankment 
or spit of gravel and sand 
near the entrance to the 
bay. Currents do not 
build spits above the water, 
but waves may build them 
up into land by washing 
material from their slopes 
up to their tops. After they 
become land, the wind may 
build dunes on them (Fig. 
251). When spits (Fig. 
249) cross bays they be- 
come bars. Along some 
coasts, as on the south side 
of Martha's Vineyard Is- 
land, such bars have closed 
the entrances to many bays. 

Reefs, spits, and the 
land to which they give 




Fig. 249. Map of harbor formed by spits; 
Plymouth, Mass. Broken lines show ap- 
proximate limits of channel. (U. S. Coast and 
Geod. Surv., Chart No. no.) 



rise, increase the irregularity of the coast-line for a time; but they 
represent the first step toward regularity, for, after the reefs have 




Fig. 250. A barrier beach with marshy tract (filled lagoon) behind it. La- 
sells Island, Penobscot Bay, Me. 

become land, the lagoons behind them are likely to be filled with sedi- 
ment washed down from the land or blown in by the wind (Fig. 250). 



35° 



COAST-LINES AND HARBORS 



Deposits of gravel and sand may be made between a mainland and 
islands near it. The Rock of Gibraltar, on the coast of Spain, has 
been thus "tied" to the mainland. 

Bars and reefs may hinder the movements of vessels, especially 
where they tend to close the entrances of harbors. A spit which does 
not obstruct the entrance to a harbor is sometimes an advantage, since 
it breaks the force of incoming waves. Spits which form harbors have 

determined the location 
of numerous villages and 
cities. The harbor of Plym- 
outh, Mass., for example, 
is protected by a spit which 
makes a natural break- 
water (Fig. 249). Prov- 
incetown, Mass., and Erie, 
Penn. (Fig. 251), have har- 
bors made by curved spits. 
Harbors. Harbors vary 
greatly in value. A good 
harbor must, first of all, 
afford shelter from stormy 
seas, must be deep enough 
for large vessels, must be 
connected with the open 
ocean by a deep channel, 
and must provide room for 
many ships. The direction whence the storm waves come and the 
direction which the harbor entrance faces have much to do with its 
safety. A harbor with a wide, unprotected entrance, facing the 
south, may be a good haven on a coast where the storm waves come 
from the east or northeast. The harbor of Gloucester (Mass.) illus- 
trates this condition. The straighter and wider the channel leading 
into the harbor, the better, for long vessels cannot navigate safely a 
narrow, winding channel. This fact alone made it necessary to open 
a new entrance (Ambrose channel) to New York harbor. The water 
near the shore should be deep enough to permit vessels to reach the 
docks, and the shore should be suitable for landings and port facilities. 
A good harbor should be free from ice. 

A harbor may have all these qualifications and yet be of little value 
commercially. Thus Casco Bay, Maine, is said to be one of the finest 




Fig. 251. Map of harbor formed by curved 
spit; Erie, Penn. Dotted areas are lines of 
sand dunes. (Erie, Penn., Sheet, U. S. Geol. 
Surv.) 



REQUIREMENTS OF GOOD HARBORS 351 

havens in the world, but Portland is one of the lesser Atlantic ports. 
For commercial importance (Figs. 252 and 253), a harbor must have 
good lines of transportation either to a large producing region, or to 
one which requires many wares from the outside world. Thus New 
York is first among Atlantic ports, not so much because of a better 
harbor, as because of its better connections with the interior, where 
many articles of commerce are produced and consumed. As a whole, 
the Pacific coast of the United States is less important commercially 
than the Atlantic coast, partly because of the broad deserts and high 
mountains which lie behind it (p. 401). 

Harbors at the mouths of large rivers are likely to have easy 
communication with the interior through river navigation, and the 
valleys are natural routes for railways. Thus important ports, like 
New Orleans (Figs. 252 and 253), Para, Calcutta, and Rangoon, are 
near the mouths of rivers which serve as highways of trade. River- 
mouth harbors, however, have many disadvantages. The current 
is a handicap for sailing vessels, which are still important in coast- 
wise commerce. Many large rivers, like the Mississippi, Amazon, 
and Ganges, have large deltas, on which the stream breaks up into 
distributaries, whose mouths may be blocked by deposits of silt and 
mud. Shallow water is common near the entrances, and this disad- 
vantage increases as larger vessels are built. Not infrequently the 
main discharge of the stream shifts from one mouth to another. 
In many rivers winding channels are kept open only by building 
jetties to direct the current. 

For these reasons expensive work has been undertaken in some cases, such as 
the building of the Eads jetties at the Southwest Pass from the Mississippi, in order 
to keep one mouth open and deep at all times. In other cases, the port developing 
in connection with a river has been located at the nearest favorable place, free from 
the disadvantages of the river mouth. Thus Marseilles is about 30 miles from the 
mouth of the Rhone, and Kurachi is some 15 miles from the mouth of the Indus. 
In each case, connection with the river, inland, is made by rail. 

Most of the important harbors of the world have been made 
by the submergence of river valleys. The harbors of New York, 
Philadelphia, San Francisco, Seattle, Liverpool, London, Ham- 
burg, Shanghai, and hundreds of others belong to this class. The 
embayed river has many advantages over such a stream as the Ama- 
zon, as the place for a commercial center. The entrance rarely shifts, 
is likely to be deep, and not infrequently tidal currents prevent its 
being filled by sediment. Water navigation also may be possible 



352 



COAST-LINES AND HARBORS 




Fig. 252. Diagram showing movement of exports from the United States by- 
coasts and leading ports, 19 10. Values are expressed in millions of dollars. Per- 
centages refer to proportion of total trade. 




Fig. 253. Diagram showing movement of imports into the United States by 
coasts and leading ports, 1910. Values are expressed in millions of dollars. Per- 
centages refer to proportion of total trade. 



HARBORS AND COMMERCE 



353 



for some distance inland. Thus boats can go from Shanghai far 
into the interior of China (p. 269), and Hamburg benefits from 
a water route which reaches the Aus- 
trian frontier. 

Many harbors on embayed coasts are af- 
fected by the deposition of sediment in or across 
their entrances (Fig. 254). The direction in 
which the entrance opens, with respect to the 
movement of shore currents, is important in this 
connection. Thus the embayed mouth of the 
Housatonic River receives the material drifted 
westward by the shore currents of Long Island 
Sound. As a result its entrance is very shallow, 
and the river mouth has no important port. 
New Haven harbor, on the other hand, is so sit- 
uated that the shore current is' turned away from 
the entrance toward deeper water. Its entrance 
is deep enough for the passage of good-sized 
vessels, and partly for this reason New Haven 
early became an important shipping center. On 
some coasts where harbors occur only at rather 
long intervals, jetties have been built to over- 
come the action of shore currents (Fig. 255). 
Galveston harbor has been improved in this way. 

Fiords are numerous along some 
coasts, but they are relatively unimpor T 
tant as sites for large ports, partly 
because many fiords are in high lati- 
tudes where commerce is not very 
important, and partly because of the 
character of the fiords themselves. 
Many are too deep for anchorage in 
the main channel, their land borders 
are too steep and high for the growth 
of a large port, and they are associated 
in many cases with mountains which 
hamper communication with the interior 
(Fig. 176). The quiet upper waters of 
fiords, however, afford good protection 




Fig. 254. Map of river 
mouth with shallow water over 
the bar at the entrance; Cal- 
casieu Pass, La. Dotted lines 
indicate 6 foot depth. Broken 
line indicates 12 foot depth. 
Figures give depth in feet. The 
channel across the bar changes 
with every gale, so that stran- 
gers are warned not to enter 
without a pilot. (U. S. Coast 
and Geod.Surv., Chart N0.202.) 



from storm waves, and every primitive 

people occupying a fiord coast early developed the sea-going habit. 

Lagoon harbors may be produced by the formation of barriers, or 

by the growth of coral reefs. ,The former are numerous along the 



354 



COAST-LINES AND HARBORS 



NANTUCKET 
SOUND 



Atlantic and Gulf coastal plains, but, except where combined with 
sunken coast-lines, few attain commercial value. The water off shore 
is rarely deep, most of the inlets are narrow and shallow, and many 
have such strong tidal currents as to prevent the ready passage of 

small craft. The inlets also 
may be closed by sediments 
deposited by waves and 
currents, unless protected 
by artificial works. The 
lagoon, even if deep origin- 
ally, or dredged to a sat- 
isfactory depth, tends to 
become shallower through 
the deposition of sediment. 
Most lands bordering la- 
goons are low and marshy 
on the mainland side, with 
only a low, sandy island, ex- 
posed to winds and waves, 
on the ocean side. Neither 
is well fitted to be the site 
of a great port. Galveston 
is the best example of a 
port with a lagoon harbor; 
large sums have been spent 
to develop and maintain 
both the harbor and the 
city. Lagoon harbors due 
to coral reefs or atolls are 
fairly numerous in tropical 
waters, especially in the 
South Pacific, but are of 
little importance, because most of them are associated with small 
islands, which have little commerce. The Great Barrier Reef of 
Australia harms rather than helps the commerce of that country. 

Few harbors are suited naturally to all the demands of present-day commerce. 
Crooked channels must be straightened, and narrow and shallow channels must be 
dredged. The opening of the Ambrose channel in New York harbor is an example. 
This new entrance to the leading Atlantic port of the United States involved the 
improvement of an old channel which had a depth of only 16 feet at low tide. 







Fig. 255. Map of harbor maintained by 
jetties; Nantucket, Mass. Broken lines indi- 
cate approximate course of channel. (U. S. 
Coast and Geod. Surv., Chart No. m.) 



IMPROVEMENT OF HARBORS 355 

This depth was enough for light-draft vessels, like scows and towboats, but the 
need for a better entrance led to the deepening and widening of the channel so 
that it now has 40 feet of water at low tide, and a width of 2,000 feet for a length 
of seven miles. The work was done by powerful dredges at a cost of about six 
million dollars. In a single year more than 600 trips were made by vessels of 
such size that, before the opening of the new channel, they could have entered 
only by lightering, or by waiting for very high tide. The channel from Philadelphia 
to the sea must be dredged to a depth of 35 feet in order to admit the largest ocean 
vessels. A plan is on foot to make a new port at the eastern end of Long Island, 
to accommodate steamers having such a length that docking facilities are no 
longer convenient in the limited space along the New York water front. 

In many places the demands of commerce from lands bordered by regular 
coasts compel the spending of large sums for artificial harbors. Dover, England, 
has one of the greatest artificial harbors in the world. There a series of concrete 
breakwaters more than two miles long enclose a harbor of nearly one square mile, 
with a minimum depth of 40 feet. The harbor cost more than $20,000,000. Its 
chief value is as a base for naval vessels at a strategic point on the English coast. 
A breakwater nearly two miles long has been built at Hilo, Hawaii, to protect 
shipping from the northeast trades. Similar extensive additions have been made 
recently to the works at Madras, to make that port equal to the other commercial 
centers of India. 

To keep pace with the ever-increasing demands of commerce, large appropria- 
tions are made annually by our federal government. From the standpoint of 
commerce, harbor improvement is one of the most important phases of govern- 
ment work. 

Many ports once important have declined because of the changing 
conditions of commerce. Thus the discovery of the all-sea route to 
India in 1497 shifted the main scene of commerce from the Mediter- 
ranean to the Atlantic coast of Europe. Mediterranean ports, like 
Venice, declined to such an extent that they almost ceased to be 
factors in the handling of European commerce. The opening of the 
Suez Canal (1869), however, made the Mediterranean the shortest 
route for trade between western Europe and the Orient; it led to a 
great expansion in the volume of commerce between those regions, 
and gave a new stimulus to Mediterranean ports. 

A similar condition is found in the Caribbean Sea and the Gulf 
of Mexico. These bodies of water bear to the Atlantic and the Amer- 
icas a relation resembling that borne by the Mediterranean to the 
same ocean and the continents of the Old World. Here also a narrow 
isthmus blocks communication with the Pacific. The Panama 
Canal, however, will open this route. By shortening the distance 
from our Atlantic ports to most Pacific points, it will make the Carib- 
bean a more important highway, and lead to increase of trade be- 
tween the two oceans. The neighboring ports, like those along 



356 COAST-LINES AND HARBORS 

the Gulf coast of the United States, will be stimulated by new traf- 
fic destined for Pacific points; they are also likely to benefit much 
as handling centers, on account of their position as way-stations 
between the populous countries of the East and West. Many Pacific 
ports will be benefited similarly by freer communication with the 
Atlantic. 

Questions 

i. Why is Holland better situated than Belgium for carrying on sea trade? 

2. Why are the natives of the Malay archipelago expert boatmen? 

3. Why is the location of Montreal better than a place at the entrance to the 
Gulf of St. Lawrence for the development of a seaport? 

4. What dangers threaten vessels plying along submerged coasts? Along 
recently elevated coasts? 

5. How would a submergence of 500 feet affect the Mississippi River system? 

6. How can the direction of shore currents be determined from the outline 
of the coast? Explain in the case of Cape Cod. 

7. Why are there few important commercial centers on the coast between 
Cape Henry and Cape Florida? 

8. What prevents Portland, Me., from being a leading commercial center? 

9. Classify the leading seaports of the United States according to the kinds 
of harbors which they possess. 

10. Why are some harbors in tropical regions, as Manila harbor, well pro- 
tected at one season and not at another? 

11. Which Gulf ports are likely to benefit most from the opening of the 
Panama Canal? Why? 

12. Why would fishing villages be more likely to develop along the coast 
shown in Fig. 241, than along that shown in Fig. 240? 

13. Suggest the probable course of shore currents along the coasts shown in 
Figs. 251 and 255. Which harbor is likely to be affected the more seriously by 
shore currents? Why? 

14. Suggest reasons why New York is a great exporting and importing city, 
and why Galveston exports much but imports little. 



CHAPTER XX 

DISTRIBUTION AND DEVELOPMENT OF THE LEADING IN- 
DUSTRIES OF THE UNITED STATES 



Agriculture 

Importance of agriculture. Agriculture is the most funda- 
mental industry of the United States; it furnishes, directly or in- 
directly, most of what we eat and wear, and other needs are less 
important than food and clothing. More than ^3 of the wage-earners 




CtVSUS-/900 



Fig. 256. Wage-earning population in agricultural pursuits in each state in 
1900 shown by inner black circle, and by the smaller number adjacent; wage- 
earning population in all pursuits shown by the outer ring, and by the larger 
number adjacent. Numbers = thousands of wage-earners. (After Middleton 
Smith.) 

of the country are engaged in agriculture (Fig. 256). The total value 
of farm lands increased about }i between 1900 and 1905, and in 1910 
amounted to more than $28,000,000,000. About half the farm lands, 
or approximately one-fourth the area of the country, is cultivated. 

357 



358 



DISTRIBUTION OF INDUSTRIES 



Fig. 257 shows the relation of improved acreage to total farm acreage 
(including woodlots, etc.) in the different states. 

The total value of all farm products has increased each year for 
more than a decade, and reached nearly $9,000,000,000 in 19 10. 



a?" 



2.6 I L OS l™» 

12.0 \ 1.9 I 5.1 

® ' G) 

VV 125.8 



feV 







07 W 



/l 9.6 /.4.7 , 



L® 



UNITED STATES 
FARM ACREAGE 839 MILLION 
IMPROVED ACREAGE 414MILLI0N 



Fig. 257. Map showing relation of improved acreage (black circles) to total 
farm acreage (outer rings) in the different states in 1900. The smaller numbers 
adjacent to the circles = millions of acres of improved land; the larger numbers = 
millions of acres of farm land. (After Middleton Smith.) 

This was more than double the figure for 1900 (Fig. 258). In 1910, 
the six crops leading in value were corn, cotton, hay, wheat, oats, 





billions of Dollars 

1434 5*789 


1870 ■ 














I88O 




















1890 




























1900 




















1 1 1 1 1 1 1 1 1 



Fig. 258. Diagram showing total value of farm products in the United States 
for the census years 1870-1910. 

and potatoes. The United States produces about 4 /s of the corn 
of the world, V5 of the cotton, J U of the oats, and Vs of the wheat. 



IMPORTANCE OF CORN CROP 



359 



The leadership of the United States in agriculture is due to (i) the 
extent, variety, and high average fertility of its soils; (2) the favorable 
climate of most sections, with range sufficient to favor the produc- 
tion of many crops; (3) the facilities for marketing products; (4) the 
energy and ability of the farming people as a whole; and (5) the 
activity of federal and state agencies in introducing new plants, 
better seeds, and scientific methods of cultivation. 

Leading Crops 

The general distribution of crops throughout the United States is 
controlled largely by climate (pp. 119, 121, 127, 131). Their detailed 
distribution is influenced also by soil, topography, transportation 
facilities, market conditions, and other factors. It is practicable to 
consider here only the leading crops. 

Corn. Corn is our most important crop — in total value, 
acreage, and amount grown. More than 300 varieties of corn are 





/. 


/ ■' 
i. 








\ \ UNITED "STATES 

V. / 2.184 MILLION 

w BUSHELS 


I I 
,0 . 1 

i 1 

10. I 

/ 3 


2. 1 






169^^ *. 


•V 


/ ' 1 


• 




\ • f 



Fig. 259. Average annual production of corn in the different states (1 899-1 908). 
Figures in states represent production in millions of bushels. (After Middleton 
Smith.) 

known, but only a few are grown in large amount. The leading 
varieties thrive best where there are plentiful rains with prevailingly 
warm, sunny weather during the growing season, and in rich, well- 
drained soils. The "corn belt" is south of the "wheat belt," be- 



360 DISTRIBUTION OF INDUSTRIES 

cause the staple varieties of corn require a higher temperature and 
a longer warm season. Illinois, Iowa, Nebraska, Missouri, Kansas, 
and Indiana are the leading corn-producing states (Fig. 259). The 
average yield of corn per acre is about 25 bushels. Experiments 
show that this can be doubled at least by the general adoption of 
better methods of tillage, careful selection of seed, and the use of vari- 
eties best suited to the places in which they are grown. During the 
last five years the corn crop of the United States has averaged nearly 
2,700,000,000 bushels. 

Because of the low price of corn, compared to its bulk and weight, 
little is shipped to distant markets. Most of it is used where it is 
grown, to feed stock. Corn is used also as a breadstuff, and in the 
manufacture of whiskey (p. 389), glucose, and other products. 

Corn appears to be a native of the highlands of Mexico, whence its cultiva- 
tion spread northward and southward at an early date. The colonists found it 
cultivated more or less by many of the Indians, and in many cases they promptly 
began to grow it. A number of the successful English settlements of eastern 
United States probably would have failed but for this food plant. As settlement 
spread westward, corn was the staple crop of much of the frontier. It was easy to 
cultivate, and usually returned a relatively large yield. It was stored easily, 
easily prepared for food, and was nourishing both for animals and man. "The 
progress of our conquest of this continent would have been relatively slow had 
it not been for the good fortune which put this admirable food plant in the posses- 
sion of our people." 

Wheat. In the United States, wheat is the most important 
food plant. It probably originated and was cultivated first in 
Mesopotamia, but its culture spread in prehistoric times into other 
parts of Asia, and into Europe and North Africa. Its great value 
as food, the comparative ease with which it can be transported 
(Why?), and its power to adjust itself to new conditions, favored its 
wide and rapid dispersal. As a result of long cultivation and selec- 
tion under different conditions, there are now more than 1,000 vari- 
eties of wheat, adapted to rather diverse conditions. 

Wheats are commonly classified as spring and winter wheat, red, white, hard, 
and soft. In the northern interior states spring wheats chiefly are grown, for 
plants from seeds sown in the fall are "winter-killed"; farther south, much winter 
wheat is raised. In general, soft wheats, relatively rich in starch, are used in mak- 
ing flour, while the very hard kinds, rich in gluten, are used chiefly for the manu- 
facture of macaroni (p. 1 28). The last is especially true of the durum wheat grown 
in the western Great Plains (p. 173). Hard and soft varieties are commonly mixed 
in making flour. The chief white wheat district is in the Pacific coast states. 



■ 



THE WHEAT CROP 



361 



Fig. 260 shows the average annual production (1899-1908) 
of wheat in the different states. The total wheat crop of the 
country in 191 1 (more than 650,000,000 bushels) was nearly 




UNITED STATES 

640} MILLION 

BUSHELS 



Fig. 260. Average annual production of wheat in the different states (1899- 
1908). Figures in states represent production in millions of bushels. (After 
Middleton Smith.) 

seven times as great as that of 1850. This increase Was due 
to (1) the demands of the increasing population, (2) the occupa- 
tion of new areas suited to wheat culture, (3) the improvement and 
general use of farm 




machinery, and (4) the 
improved conditions 
for storing, transport- 
ing, and milling the 
grain. As in the case 
of most other crops, 
the average yield per 
acre of wheat in the 
United States can be 
increased greatly. For 

the ten years 1897 to 1906, inclusive, it was 13.8 bushels; during the 
same time it was 32.2 bushels in the United Kingdom, 28 in Ger- 
many, and 19.8 in France. During recent years the exportation of 



Fig. 261. Map showing centers of production 
of corn, wheat, and oats (1 850-1 900). 



362 



DISTRIBUTION OF INDUSTRIES 



wheat from the United States has decreased, as the demands of the 
home market have increased. While the acreage devoted to wheat 
culture in the United States can be increased in the semi-arid sections, 
and wheat may be imported, the greater supply needed in the future 
must be obtained chiefly by securing larger yields where wheat is 
already grown. The centers of cultivation for wheat and the other 
leading cereals have moved steadily westward (Fig. 261). 

Other cereals. Oats thrive best in a moist and relatively cool 
climate. They do fairly well in some of the southern states, where 
the climate, though warm, is moist, but do not grow well where it 




UNITED STATES 
S49 MILLION 
BUSHCLS - 



Fig. 262. Average annual production of oats in the different states (1899- 
1908). Figures in states represent production in millions of bushels. (After 
Middleton Smith.) 



is both warm and dry. The chief area of production is in the north- 
ern Interior (Fig. 262). In recent years the total oats crop of the 
country has averaged nearly a billion bushels. A small part of the 
crop is used as food for man, chiefly in the form of oatmeal ; most 
of it is used as feed for animals. 

Although barley can be grown successfully under a wider range 
of climatic conditions than either wheat or corn, its cultivation in 
the United States is confined largely to the region west of Lake 
Michigan (from Wisconsin to the Dakotas), and to the Pacific coast. 
In the order of their importance, the leading states are California, 



COTTON CULTURE 



363 



Minnesota, Wisconsin, North Dakota, Iowa, South Dakota. In 
the northern Interior the barley is used chiefly for the manufacture 
of malt liquor (p. 389), and on the Pacific coast for feed. 

Among the minor cereals grown in the United States for their 
grains or for forage are rice (Fig. 263), rye, buckwheat, kaffir corn, 
and millet. 

Hay. Hay includes various grasses and legumes which are 
" cured" as food for stock. The more important ones are timothy, 
clover, and alfalfa (p. 297). Some of the cereal grasses, like oats and 
barley, sometimes are grown for hay. Hay is produced in every 




UNITED STATES 

832,607 THOUSAND 

POUNDS 



Fig. 263. Average annual production of rice in different states (1904-1908). 
Figures represent production in thousands of pounds. (After Middleton Smith.) 

state, but the chief area is in the eastern half of the country, north of 
the 37th parallel. Although alfalfa is cultivated chiefly in the western 
part of the country, it probably will become of importance in the 
middle states in the near future, because of its relatively large yields, 
its high nutritive value, and its importance in increasing the amount 
of nitrogen in the soil (p. 29). 

Cotton. The cotton of commerce is the fiber which surrounds 
the seeds of the cotton plant. The value of the fiber and the uses 
to which it is put depend on its length (y£ to 2^ inches), strength, 
fineness, and color. The cotton plant requires a warm, moist climate, 
and a relatively long season free from frost. These are the principal 
factors which limit the cotton-producing area of the United States to 
the southern part, east of the Great Plains (Fig. 264). In some 
other countries, the area of cotton culture may be extended. Sea- 
island cotton, characterized by its long, fine fiber, thrives best on cer- 
tain islands off the South Atlantic coast, partly because of the high 



364 



DISTRIBUTION OF INDUSTRIES 



humidity. Sea-island cotton is also grown some distance inland in 
southern Georgia and northern Florida. In general, the largest 
yields of cotton are obtained on the alluvial soils of the valley bottoms, 
and on the limey soils of the coastal plain (p. 171). During the last 
five years the total cotton crop of the country has averaged more 
than 12,000,000 bales. About y$ of the cotton grown in the United 
States is manufactured at home (p. 387) ; the rest is exported. 

The cultivation of cotton in the United States began in the colonial period, 
but increased slowly until after the invention of the cotton gin (Eli Whitney, 1792) 
in this country, and of spinning machinery in England. The former made easy 
the separation of the fiber from the seed, enabling one man to do as much as 100 















s 38 \ j /* — { ,r • 


■ j 2 


(540 




■res Y 5 ^4ft' 




*• 


Su^**4j3«t ^^^*^\$ 2 \ 


ipr 






V 1 


UNITED STATES 

I0.B48 THOUSAND 
BALES 



Fig. 264. Average annual production of cotton in different states (1899-1908). 
Figures represent production in thousands of bales. A bale is 400-500 pounds. 
(After Middleton Smith.) 



to 200 could do by hand. These things, coupled for some years with unusually 
high prices for cotton, caused a great increase in its production. The develop- 
ment of the cotton industry meant also a greatly increased demand for slaves as 
field hands. The work in the cotton fields was simple, requiring little skill and few 
tools. In these and other ways it was adapted to slave labor, and, as years passed, 
cotton culture and slavery became mutually dependent. They became, too, 
dominant factors in the economic, social, and political life of the southeastern 
states, and helped to separate their interests in many ways from those of the 
northern states. Thus, the New England cotton manufacturer (p. 387) demanded 
a tariff on imported goods to protect him against foreign competition; the southern 
cotton planter, who bought many of his supplies abroad, was injured by the tariff, 
and of course opposed it. The growing sectionalism between the North and South 
resulted in the Civil War. 

Other vegetable fibers. Of the several plants besides cotton 
which are grown for fiber, only hemp and flax are cultivated to any 
large extent in the United States. Indeed, the latter is cultivated 



VEGETABLES AND FRUITS 



365 



here almost entirely for its seed, from which linseed oil is obtained. 
In Russia and some other places, flax is produced chiefly for the inner 
bark fiber, from which linen cloths are made. The fiber of hemp is used 
to make twine, rope, bagging, etc. Although both plants can be grown 
under rather a wide range of conditions, the cultivation of hemp in 
this country is confined largely to Kentucky, and that of flax chiefly 
to the Dakotas, Min- 
nesota, and Montana. 

Tobacco. The 
United States produces 
about ^3 of the tobacco 
of the world, its crop 
in 191 1 being about 
800,000,000 pounds. 
It is grown in most 
states east of the 97th 
meridian, but a few 
produce the bulk of the 
crop (Fig. 265). The 
quality of the product 
varies greatly with the 
conditions of soil and 
climate, and with the 
care used in selecting 
the seed, cultivating 
the plants, and curing 
the leaves. Many 
grades are produced. 

Vegetables and fruits. The growing of vegetables and fruits 
for distant markets and for food throughout the year has become an 
important industry mainly as a result of (1) improved transportation 
facilities, especially refrigerator cars, and (2) the development of the 
canning industry (pp. 379, 386). It is impracticable to consider here 
the many fruits and vegetables now grown for commercial purposes 
in the United States. Some have been mentioned (pp. 119, 297, 298). 
Potatoes rank first in value among vegetables, and apples among 
fruits; the cultivation of both is distributed widely. 

The influence of refrigerator cars on the rise of industries involving the ship- 
ment of perishable foodstuffs has been very great. The fruit and vegetable indus- 
tries of the South and the deciduous fruit industry of the far West owe their 



Q^\ , 






\ ^^K^p/Hf 






7 f 52843 

1 _s* 




7 Jlilk 








C86I 


\ [54355 


*l 


1486 \ 
• 7 




659 %}S^^r-^\ 


\39 L— 




L • \ 

V 43l \ UNITED STATES 

X } 740.356TH0USAND 
V POUNDS 



Fig. 265. Average annual production of tobacco 
in different states (1 900-1 908). Figures represent 
production in thousands of pounds. (After Mid- 
dleton Smith.) 



366 DISTRIBUTION OF INDUSTRIES 

development largely to the refrigerator car. It has enabled California, though 
one of the states farthest from the chief city markets, to become the leading fruit- 
growing state (p. 297). 

In many places, the refrigerator car helped change various fruits and vegetables 
from luxuries, obtainable during a short season only, to staple articles of food 
available during a long season, or throughout the year. For example, New York 
City formerly obtained cantaloups during a few weeks only from New Jersey, 
Delaware, and Maryland. Now the season for them in New York lasts from early 
May to late October, and some of them come from the Pacific coast. 

Sugar plants. Sugar-cane is a tropical and sub-tropical plant, 
and its cultivation in the United States is confined to the Gulf States, 
Georgia, and South Carolina. Louisiana grows more than 9 /io of 
the total crop of the country. In 191 1, 690,000,000 pounds of cane- 
sugar were produced in the United States. 

The sugar-beet was brought to this country some forty years 
ago from central Europe, and in recent years its cultivation has 
spread rapidly. California, Michigan, Colorado, Utah, Idaho, and 
Wisconsin lead in the production of sugar-beets, but the industry 
has some importance in a dozen other states. In the West, sugar- 
beets are grown largely on irrigated lands. The production of 
beet-sugar in the United States increased about sixfold between 
1900 and 191 1, amounting, in the latter year, to more than 
a billion pounds. 

Animal Products of Farm and Range 
Cattle. Cattle are raised in the United States chiefly for beef, 
dairy products, and hides. Fig. 266 shows that most of the milch 
cows are in the more densely settled eastern half of the country, and 
that in the eastern half, most are in the northern states. The many 
cities and villages of the North Atlantic and North Central States 
require an enormous quantity of milk, and cannot draw their daily 
supplies from great distances. Herds may be kept at a greater 
distance from market in connection with the manufacture of butter, 
cheese, and condensed milk (p. 386). 

Fig. 267 indicates the distribution of cattle other than milch 
cows. This map differs from the preceding one in the smaller 
numbers for the North Atlantic States and the greatly increased 
numbers in the Great Plains and western states. Large parts of 
the Great Plains afford the best environment for cattle in the 
country, and much of the land, furthermore, cannot be used for 
growing crops (p. 329). Extensive areas are required for grazing 



THE CATTLE INDUSTRY 



367 



large herds of cattle, and with the growth of population in the 
East much land so used in earlier years has been devoted to other 
purposes. The United States has about V7 of the world's cattle. 




UNITED STATES 
17.987 THOUSAND 
MILCH COWS 



Fig. 266. Milch cows on farms and ranges. Average annual number in 
thousands (1899-1908). (After Middleton Smith.) 




UNITED STATES 
42.650.THOUSANO 
CATTLE.. 



Fig. 267. Cattle other than milch cows on farms and ranges. Average 
annual number in thousands (1 899-1 908). (After Middleton Smith.) 



3 68 



DISTRIBUTION OF INDUSTRIES 



Sheep. Sheep are raised for mutton and wool. During the 
last fifty years a great change has occurred in their distribution. 
The number in most of the middle and eastern states has decreased, 
while in the western states it has increased greatly. At the beginning 
of the period, the West had less than Vio of the sheep of the country; 
now it has more than Yi (Fig. 268; What are the probable reasons 
for the change?). The annual wool clip of the United States is more 




UNITED STATES 

52,206 THOUSAND 

SHEEP. 



Fig. 268. Sheep on farms and ranges. Average annual number in thousands 
(1899-1908). (After Middleton Smith.) 



than 300,000,000 pounds; nearly all of it is used in American fac- 
tories, and in addition much is imported. 

Swine. About 2 /s of the swine of the world are in the United 
States. While they are raised more or less in every state, the great 
swine region (Fig. 269) is the same as the leading corn-producing 
section (Fig. 259), for corn is the chief food for swine. Nearly half 
the corn crop is disposed of in this way. 

Horses. A comparison of Fig. 270, showing the distribution of 
horses in the United States, with Fig. 257, showing the improved 
acreage and its relation to the total farm area in the different states, 
indicates that the number of horses in the different states corresponds 
roughly to the amount of land cultivated. This is less striking in 
some of the southeastern states, where many mules are used to cul- 



SHEEP, SWINE, AND HORSES 



369 



tivate the land, because they can stand hard work in that climate 
better than horses. 

The total value of farm animals in the United States in 1910 was 
about $5,000,000,000. 




UNITED STATES 

48.565 THOUSAND 

SWINE.. 



Fig. 269. Swine on farms and ranges. Average annual number in thousands 
(1899-1908). (After Middleton Smith.) 




UNITED STATES 

16, 929 THOUSAND 

HORSES. 



Fig. 270. Horses on farms and ranges. Average annual number in thousands 
(1899-1908). (After Middleton Smith.) 



37° 



DISTRIBUTION OF INDUSTRIES 



Poultry and eggs. Poultry and eggs are incidental products 
of most farms. In recent years poultry-raising has become also 
a specialized industry of importance, particularly in the leading 
corn-producing states and near some of the larger cities. The value 
of the poultry and eggs produced yearly in the United States is nearly 
$300,000,000. 

Forest Resources and Lumbering 

The forests of the United States have been a chief factor in the 
progress of the country. They have furnished firewood and materials 
for buildings, furniture, implements, utensils, vehicles, fences, paper, 




FOREST REGIONS 

OFTHE 
UNITED STATES 

The Unshaded Areas are Treeless 
Except Along the Streams 



Fig. 271. Map showing forest regions of the United States. Not all the land 
within the shaded areas had forests, and much has been cleared. The unshaded 
areas have few forest trees. (U. S. Forest Service.) 

posts, poles, cross-ties, ships, railroad cars, bridges, sidewalks, etc. 
Our dependence on the forests for material for many things is less 
than formerly. Thus, coal is now used extensively as fuel; brick, 
stone, and cement for buildings; iron and steel for ships, freight 
cars, bridges, etc.; wire for fences; and cement for sidewalks. Never- 
theless, the yearly drain upon the forests has increased rapidly. 
The United States is the leading wood-producing country, and it is 
estimated that its total annual consumption (including that de- 



FOREST RESOURCES AND LUMBERING 



37i 



stroyed by forest fires) may amount to 100,000,000,000 or more board- 
feet. 1 The total value of the forest products in 1909 is estimated at 
about $1,250,000,000. 
Forest regions of 
the United States. 
Forests still cover 
about % the area of 
the United States. 
Although the present 
forest land is more than 
3/5 the original area, the 
amount of good timber 
remaining probably is 
not more than half the 
original amount. This 
is very significant in 
view of the compara- 
tively short time the 
forests of the country 
have been supplying 
timber. Fig. 271 shows 
the five great forest 
regions of the country. 

(1) The Northern For- 
est contains both soft and 
hard woods, though the for- 
mer have been most impor- 
tant. The leading kinds 
of trees include white pine, 
red pine, spruce, hemlock, 
cedar, balsam-fir, birch, 
cherry, and sugar maple. 
(2) The Hardwood Forest 
contains oak, elm, hickory, 
cottonwood, maple, bass- 
wood, chestnut, ash, etc., 
not all of which are hard. 

Cottonwood and basswood, for example, are soft. (3) In the Southern Forest the 
yellow pine predominates, but in places suited to their growth are cypress, oak, 
gum, magnolia, and other hardwoods. (4) The Rocky Mountain Forest is almost 
entirely coniferous; leading trees are the western yellow pine, lodge-pole pine, 
Douglas fir, larch, spruce, and western red cedar. (5) The Pacific Forest is also 

1 A board-foot is a piece of wood one foot square and one inch thick. 





Billions of Feet 
1 2 3 4 5 


Yellow Pine ) 












I 

Doug. Fir. . . 
Oak 

White Pine.. 
Hemlock.... 

Spruce 

Western Pine 




■ 






























































Maple 

Cypress 

Yel. Poplar. . 
Red Gum . . . 
Chestnut.... 
Redwood. . . . 

Beech 

Birch 

Basswood . . . 

Elm 

Cedar 

Hickory .... 

Ash 

Cottonwood. . 

Larch 

Tamarack . . . 
Balsam Fir.. 
Sug. Pine . . . 

Tupelo 

White Fir... 
Sycamore . . . 

Walnut 

Cherry ..... 
Lodgep'l. Pine 
Allothers... 














1 
1 



Fig. 272. Diagram showing lumber cut for 1909, 
by kinds of wood. (U. S. Forest Service.) 



372 



DISTRIBUTION OF INDUSTRIES 



coniferous, consisting chiefly of Douglas fir, western yellow pine, redwood, western 



red cedar, sugar pine, etc. Fig. 272 shows 







Billions of Feet 




1234 


Wash.. 
La ... 
Miss.. . 
N.C... 
Ark... 
Va..;. 
Tex... 
Wis... 
Ore.... 
Mich. . 
Ala. . . 
Minn. . 
Penn.. 
W. Va. 
Ga.... 
Tenn. . 
Fla.... 
Cal.... 
Me.... 
S. C... 












































































































m^mmm 


Ky.... 










N.Y... 










Mo.... 










N.H.. 










Ida.... 










Ind.... 










Ohio... 


Mam 








Mass.. 


Hi 








Vt 


m 








Mont. . 


■i 








Md.... 


■1 








Okla... 


■ 








IU 










Conn.. 










Col.... 


■ 








Iowa . . 


■ 








N.M.. 


■ 








Ariz. . . 


1 








N.J... 


1 








Del.... 










S. D... 










Wyo... 










R. I... 










Utah.. 










Kas .. 










1 



Fig. 273. Diagram showing lumber produc- 
tion by states in 1909. (U. S. Forest Service.) 



the lumber production for 1909, 
by kinds of wood. The cut of 
yellow pine equaled that of 
the four next most important 
kinds; white pine, long in 
the lead, ranked fourth. These 
facts reflect the recent rapid 
growth of lumbering in the 
southern and western states, 
and its gradual decline in the 
Lake states. 

Distribution of the 
lumbering industry. As 
would be expected from the 
distribution of the forests, 
lumbering is carried on in 
every state, but, as Fig. 
273 shows, the production 
varies greatly. For many 
years the northeastern 
states, especially Maine 
and New York, led in lum- 
bering. Since 1850, the in- 
dustry has declined greatly 
in that region. The forests 
of the Great Lakes region 
were the next to be used 
extensively (p. 283), fur- 
nishing in 1880 about Vi 
the lumber cut of the 
country. Michigan and 
Wisconsin became, each in 
turn, the leading lumbering 
state; now they rank tenth 
and eighth, respectively 
(Fig. 273). At present, the 
southern states contribute 
most to the lumber output 
(Fig. 273); but the indus- 
try is expected to reach its 
climax there within a few 



CONSERVATION OF FOREST RESOURCES 373 

years, and already the Pacific states are large producers. Indeed, 
Washington is now the leader. 

Conservation of forest resources. About 260 cubic feet of 
wood per capita per year are consumed in the United States. This 
is greater than the rate of consumption in any other country, about 
ten times that in France, and seven times that in Germany. Stated 
in another way, we are taking, on the average, 40 cubic feet of wood 
per acre per year from our forests. Since the average growth in the 
forests of the United States is not at present more than 1 2 cubic feet 
per acre per year, we are consuming wood more than three times as 
fast as it is grown in our forests. The United States cannot in the 
long future count on foreign sources of supply for ordinary structural 
timber, for other countries probably will need all they can grow. 
Therefore, if there is to be a permanent supply of wood in this 
country, we cannot long continue to use more than our forests 
produce. Clearly, every means of reducing the drain upon the 
forests, and every means of increasing their production, should be 
encouraged. 

Altogether apart from a supply of timber, the preservation of 
forests in many places is desirable (1) to reduce soil erosion and the 
resultant deposition of waste on lower lands, in stream channels, and 
in harbors (p. 167) ; (2) to make floods less frequent and less dangerous 
(p. 237); and (3) to help equalize the flow of streams important for 
navigation, power (p. 290), or irrigation (p. 298). 

The principal ways in which the forest resources of the United States should 
be conserved may be indicated briefly. (1) Losses from fires should be reduced 
(Fig. 274). The average annual loss of merchantable timber is estimated at about 
$50,000,000. In addition, many lives have been lost in some forest fires, and 
villages have been consumed, (b) Great loss is involved in the damage to young 
trees and seedlings, (c) After high-class timber is burned off an area, the latter 
may be occupied by inferior kinds of timber, (d) The humus in the soil may be 
consumed, reducing or destroying the fertility of the latter, (e) Erosion may 
increase on burned- over areas, and the flow of streams may become more uneven. 
Forest fires are started by sparks from locomotives, by careless campers and 
hunters, by careless clearing and brush burning, by lightning, and in other ways. 
Save those due to lightning, nearly all may be prevented. So far as its funds 
permit, the Forest Service maintains a patrol in the National Forests, partly with 
a view to detecting fires at their beginning, and fighting them while they are 
still small. Some state and private forests also are patrolled during the dry 
season. 

(2) Waste in logging should be reduced so far as practicable. At present it 
averages about 25% in the timber holdings of individuals and companies, and 
something less than 10% in the National Forests. In connection with logging 



374 



DISTRIBUTION OF INDUSTRIES 



operations, young trees should be protected, and seed trees should be left. (3) 
The wastes in sawmills and wood-using industries should be reduced. (4) Refuse 
wood may be used in making many things now manufactured from good timber. 
(5) Wherever practicable, forest areas should be kept fully stocked with rapid- 
growing and valuable species of trees. In this way the production of wood in 
existing forests may be increased greatly. (6) In many places, cut-over or burnt- 
over areas should be reforested. (7) Posts, poles, cross-ties, mine timbers, pilings, 




Fig. 274. Effects of hurricane and fire in a heavy stand of white pine on the 
Little Fork of St. Joe River, Cceur d'Alene National Forest, Idaho. (U. S. Forest 
Service.) 



shingles, etc., may be treated with some preservative substance, such as creosote, 
and thus rendered less subject to decay and to the attack of insects. Wood treated 
in this way lasts 10 to 18 or more years longer than wood not so treated. The 
general adoption of the practice of treating with preservatives wood used in the 
above ways would not only lessen the drain on the forests, but also give value to 
much inferior timber. (8) The enormous waste of forest resources caused by in- 
sects can be reduced greatly. (9) The wasteful methods generally followed in 
the turpentine industry (p. 380) should be abandoned. (10) For many purposes, 
other material may be substituted advantageously for wood (p. 176). (11) Recently 
much has been done to conquer the diseases of forest trees, and much more may 
be done in the future. (12) Standing timber is taxed in most states each year, 



I 



NEW ENGLAND FISHERIES 375 

and this leads owners in many cases to cut all their timber and put it on the 
market as soon as possible. Before the principles of scientific forestry can be 
adopted generally, these tax laws must be reformed. 



The Fishing Industries 

Nature and general distribution. Fishing on a commercial 
scale is carried on from many places on the coasts of the United 
States, and on many inland streams and lakes. The total annual 
value of the products of the fisheries has exceeded $60,000,000 in 
recent years, the products of the coast and ocean fisheries making 
nearly ^ of the total. The products include not only food-fishes, 
but the commercial products derived from all other marine and 
fresh-water animals. About 2 /$ of the products are furnished by 
animals other than fishes, such as clams, oysters, lobsters, shrimps, 
sponges, whales, and fur-seals. The leading fish of commercial im- 
portance are salmon, cod, shad, menhaden, mackerel, squeteague (or 
sea trout), haddock, herring, and trout. 

Most marine fishing industries are favored by (1) extensive areas 
of shallow water off shore, to serve as feeding and breeding grounds 
for large numbers of fish; (2) convenient harbors affording safe havens 
for fishing boats; and, where the industry is dependent on the sale of 
fresh fish, (3) nearness to large centers of population. With present 
facilities for transportation and refrigeration, the last point is less 
important than formerly. 

Where poor soil, rugged surface, or rigorous climate has made farming in 
coastal regions unprofitable, the people have turned to the ocean for a living. They 
become fishermen, develop into expert sailors and navigators, and supply men for 
the great merchant fleets of the world. 

Atlantic coast fisheries. Since early colonial days, the fishing 
industries of the Atlantic coast have centered in New England, 
which had all the advantages mentioned above. Cod, haddock, 
mackerel, and herring are taken in largest quantities. 

Most of the early settlements along the eastern coast of New England had 
fishing fleets, and many of them depended almost entirely on the industry. For 
many years, cod was the leading export of New England. The better fish were 
taken to southern Europe, while those of poorer quality were sold in great quanti- 
ties in the West Indies to feed the slaves. Here salted cod was cheaper and more 
wholesome than meat, and would keep much longer. In early days many fishing 
towns were scattered along the New England coast at points where the advantages 
of harbors and nearness to good fishing grounds were combined, and the industry 



376 DISTRIBUTION OF INDUSTRIES 

was carried on chiefly from small boats near land. As the supply of fish near at 
hand was reduced, larger vessels were built for use on the distant banks, and the 
industry centered in a few places having special advantages. Gloucester has the 
best harbor on Cape Ann, and was the first fishing port of the district to secure rail- 
road connection with Boston. Accordingly, the industry developed rapidly there, 
while it declined at less favored neighboring towns. To-day, Gloucester and Bos- 
ton are the most important fishing ports in the United States. 

The whaling industry was important in New England for many years, although 
insignificant now. Several things caused its rapid decline during the third quarter 
of the last century, especially (i) the growing scarcity of whales and (2) the dis- 
covery of petroleum in Pennsylvania. 

The oyster is the most important shell-fish. It thrives best 
in relatively warm waters, and in quiet, shallow estuaries and bays, 
such as those between Long Island Sound and Chesapeake Bay. 
Some 4 /s of the oysters marketed in the United States come from this 
part of the coast. At first the industry depended entirely on natural 
beds of oysters ; but as the natural supply declined, the practice grew 
up of " planting" young oysters, and leaving them to mature. 

Pacific coast fisheries. The salmon fisheries are the most 
important ones on the Pacific coast, but cod and halibut are caught 
in large numbers. The salmon industry is centered in Alaska, 
about the shores of Puget Sound, and on the Columbia River. Most 
of the fish are caught in traps and weirs during the spring or summer 
run, when they ascend the rivers to spawn. At such times, the 
waters sometimes have been so congested with salmon that the near- 
by canneries, working night and day, have found it difficult to handle 
the fish brought in. Canned salmon is the largest fish export of the 
United States. 

In Alaska, the salmon fisheries rank next to gold mining in value of output. 
The total value of their product since 1868 is said to be more than $130,000,000, or 
more than eighteen times the amount the United States paid for Alaska in 1867. 

The largest fur-seal herd in the world uses the cool, moist Pribilof 
Islands (Bering Sea) as a breeding ground, but the estimated number 
of animals in it was reduced from some 5,000,000 in 1867 to about 
200,000 in 1905. In recent years steps have been taken to prevent 
the extermination of the herd, and to put the fur-sealing industry on , 
a permanent basis. 

Mining, Quarrying, etc. 

The principal mineral resources of the United States, together with 
their uses and economic significance, were noted in Chapter XIII. 
The mining and quarrying of these resources afford employment to 






FACTORS AFFECTING MINING 377 

hundreds of thousands of people, and furnish raw material or fuel for 
many other industries. The total value of the mineral products of 
the United States in 19 10 was about $2,003,000,000. The accom- 
panying table shows the production of the leading mineral substances 
in that year. 

Quantity Value 

Pig Iron 27,303,567 long tons $425,115,235 

Copper 1,080,159,509 pounds 137,180,257 

Gold 4,657,018 troy ounces 96,269,100 

Lead 372,227 short tons 32,755,976 

Silver 51,137,900 troy ounces 30,854,500 

Zinc 252,479 short tons 27,267,732 

Aluminum 47,734,000 pounds 8,955,700 

Bituminous coal 417,111,142 short tons 469,281,719 

Pennsylvania anthracite 75,433,246 long tons 160,275,302 

Natural gas 70,756,158 

Petroleum 209,556,048 barrels 127,896,328 

Clay products 170,115,974 

Cement 77,785,141 barrels 68,752,092 

Stone 76,5 20,584 

Other structural materials 40.821,793 

Gypsum 2,379,057 short tons 6,523,029 

Phosphate rock 2,654,988 long tons 10,917,000 

Salt 30,305,656 barrels 7,900,344 

Mineral waters 62,030,125 gallons 6,357,590 

Distribution of mineral industries. In general, the distribu- 
tion of mineral deposits (pp. 175-183) controls that of mining and 
quarrying, but whether or not a given mineral deposit can be worked 
profitably depends on several things. Chief among these are (1) 
its size, (2) its quality, (3) its location, (4) the cost of working it, 
and (5) market conditions. The relative importance of these fac- 
tors varies greatly with different minerals. 

(1) In many places minerals of value occur in quantities too small 
to mine. The opening and equipment of a modern mine might be 
justified by a small deposit of a valuable mineral, like gold or silver, 
but might not be warranted by a vastly larger deposit of a cheap min- 
eral, like iron. (2) There is much low-grade ore and coal that cannot 
be mined profitably in competition with better material of the same 
kind. For example, the United States is estimated to have more than 
75 billion long tons of low-grade iron ore, not available (i. e., not 
workable with profit) under existing conditions, as against less than 
5 billion tons which are available. (3) The importance of location 



378 DISTRIBUTION OF INDUSTRIES 

is greatest in the case of minerals which are abundant and cheap, and 
least in the case of those of great value. Thus iron ore which could 
be mined with a small profit if near the shores of the Great Lakes, 
probably could not be mined if in Utah. On the other hand, gold offers 
great value in small bulk, and so can be transported easily. In 
recent years, therefore, it has attracted thousands of men to remote 
sections of Alaska, where most other minerals could not be mined 
with profit. The discovery of gold in California in 1848 brought 
nearly 50,000 miners there in 1849, added a new state to the Union 
in 1850, and gave it a population of 360,000 in i860. (4) Relatively 
cheap minerals are mined only where they occur in favorable posi- 
tions, rather near the surface; those of greater value justify deeper 
mines and greater expense. In classifying coal lands, the United 
States Geological Survey has taken a depth of 3,000 feet as the present 
limit for coal mining. Some of the copper mines of the Lake Superior 
region are more than a mile deep. (5) The output of many mines and 
quarries is affected greatly by the demand for the product. The total 
value of the mineral products of the country declined from $2,071,- 
000,000 in 1907 to $1,595,000,000 in 1908, largely as a result of the 
business depression which began late in 1907. 

The influence of mining on the distribution of population and 
the growth of cities is discussed elsewhere (pp. 315, 330, 397, 403). 

Manufacturing Industries 

Growth of manufacturing industries. For many years, most 
manufacturing in the United States was done in homes. The cloth- 
ing, utensils, and implements used by the people were largely " home- 
made," as is still the case in certain regions (p. 309). There were 
some factories even in the colonial period, and manufactured goods 
were imported from other countries, especially for the wealthier people. 
By 1820 or 1825, the factory system was established throughout much 
of the country then settled. Since 1850, and especially since 1880, 
the manufacturing industries of the United States have grown with 
great and increasing rapidity (Fig. 275), until now it ranks first among 
manufacturing countries. The total value of manufactured products 
for the country amounted,in 1910, to more than $20,000,000,000. The 
industrial growth of the last half -century has been due to (1) the in- 
crease of population; (2) the improved financial condition and higher 
standard of living of the people; (3) the increasing supplies of raw 



INDUSTRIES LOCATED BY RAW MATERIALS 379 

materials; (4) the improvement of transportation facilities; and (5) 
the growing demand abroad for American goods. 

The Location of Industries 
Many manufacturing centers specialize in a few products. Thus 
Brockton, Massachusetts, is the leading boot and shoe center; Grand 
Rapids, Michigan, is famous for its furniture; and Peoria, Illinois, 
leads in distilling liquors. In some cases, as in those cited, the 
reasons for the development of special industries in certain places 
are clear; in others, the causes are obscure. In general, the most 





] 


trillions of Dollars 

2 3 4 5 6 7 8 9 IO 11 12 13 14 15 16 17 18 19 20 


1850 


- 


: 








































1860 








































1870 




















































1880 






















































pa 


























■■■■■■■■■■ 


\m 






















HTnTTiiiiTiTT^^ 

















Fig. 275. Diagram showing total value of manufactured products in the 
United States for the census years 1850-1910. 

important factors influencing the location of manufacturing indus- 
tries are (1) distribution of raw material, (2) command of power, 
(3) accessibility of market, and (4) a supply of labor. 

Distribution of raw material. The influence of the distri- 
bution of raw materials in locating the industries which use them is 
greatest in the case of (1) perishable raw materials, and (2) raw 
materials that are too bulky and too cheap to be carried far to fac- 
tories. (1) If prepared and handled carefully, fresh fruits and 
vegetables may be sent long distances in refrigerator cars (p. 365). 
But it is impracticable to do this with the large quantities used in 
the canning, preserving, and allied industries. Hence these indus- 
ries are located, for the most part, near the places of production. 
Thus, canning and drying fruit and making wine are important in- 
dustries in California. Indeed, California furnishes about 9 /io of the 
dried fruit and some % of the wine made in the United States. In 



3 8o DISTRIBUTION OF INDUSTRIES 

New Jersey and Delaware ^ of the total canned product are toma- 
toes. Similar influences appear in the case of many animal products. 
The centering of slaughtering and meat-packing in Chicago, South 
Omaha, and Kansas City is due partly to the losses which result 
from shipping live animals long distances. Butter, cheese, and con- 
densed milk are manufactured extensively where large quantities of 
milk are produced, as in New York, Wisconsin, and Iowa. 

(2) Among the raw materials that are too bulky or too cheap 
to be carried economically to distant points are many of the products 
of the quarries, mines, and forests. Hence the industries which use 
these materials are located in most cases near the sources of supply. 
In some cases, on the other hand, special conditions make it practi- 
cable to take bulky raw material to remote manufacturing plants. 
Thus granite from Massachusetts or marble from Vermont is shipped 
profitably for monumental purposes throughout the country, because 
when cut and polished in a local yard a single piece may have a market 
value of hundreds of dollars. Again, it may be feasible to take bulky 
raw material to distant points because of very cheap transportation, 
as in the case of the iron ore of the Lake Superior region (pp. 268, 282). 

The tendency of wood-working industries to keep close to the lumbering 
districts is indicated by the distribution of saw-mills, wood-pulp mills, the turpen- 
tine industry, charcoal burning, and, less strikingly, furniture making. The wood- 
pulp industry was most important originally in western Massachusetts, and later 
in Pennsylvania, but as the supply of pulp-wood decreased, the industry became 
more important elsewhere. It is now centered in Maine, northeastern New York, 
and Wisconsin, where spruce and hemlock, the principal woods used in the industry, 
are more abundant. These regions have the additional advantages of abundant 
water power and relatively near markets for the finished products. The manufac- 
ture of furniture was carried on chiefly in the East until some twenty years ago, 
with New York the leading center. Now Chicago stands well ahead of New York, 
and Grand Rapids is a close third (p. 288). This migration of the industry fol- 
lowed the shifting of the center of lumbering from the northeastern states to the 
Great Lakes region (p. 372). Recently, the growth of lumbering in the Gulf states 
and northwestern states (p. 372) has led to a rapid development of furniture- 
making in those sections. The manufacture of tar, pitch, and turpentine has 
long been an important industry in the South. These things are made chiefly from 
the "sap" of the long-leaf pine, and this is obtained, in most cases, by frequently 
making needlessly large cuts in the lower part of the trunk. The average period 
during which a given tree furnishes sap under this method is only four years, and 
this has caused a steady migration of the center of the turpentine industry. North 
Carolina led for a time, then South Carolina came to the front. From South Carolina 
the industry spread into Georgia, where it is beginning to decline. Now Florida 
leads, and the industry is spreading rapidly into Alabama and Mississippi. The For- 
est Service has developed new methods of obtaining the sap from smaller cuts. The 



INDUSTRIES LOCATED BY POWER 381 

general adoption of these methods will increase greatly the life of the industry. 
Most ores, except iron, have relatively high values for small bulk, but as they 
come from the mine, they are likely to be associated with much worthless material. 
Hence the metallic matter in most cases is partly separated from the waste (i.e., 
is concentrated) at the mine. It may also be smelted (metal extracted from the 
ore) at the mine, but since in its concentrated form it is commonly valuable enough 
to bear rather heavy freight charges, it is shipped in many cases to some big 
smelter, where large-scale operation reduces the cost. Refining the metal may 
be done in turn far from the smelter. Thus, silver ore mined in Leadville, Colo- 
rado, may be concentrated at or near the mine, smelted in Pueblo, refined in 
Jersey City, and manufactured into jewelry in Providence, Rhode Island. 

The source of many raw materials of high value has little if any 
influence on the location of the industries which use them. This 
is determined by other factors. 

Many illustrations might be given. The United States produces no raw silk 
for the many silk mills of New York, New Jersey, and Pennsylvania. Lowell, 
Massachusetts, manufactures large quantities of woolen goods, although New 
England now raises few sheep (p. 368). 

Influence of power resources. Available power may be the 
leading factor determining the location of manufacturing plants 
which use raw material suited to economical transportation. Water 
power determined the location of many of the older manufacturing 
centers of New England (p. 288). Some of these places had small 
power resources, and depended on the local supply of raw material; 
such places have declined. Others have continued to grow because 
they had larger power resources and were so situated that, as transpor- 
tation facilities were improved, they could use raw materials from 
increasingly distant points, and could bring in coal to supplement 
their water power. There are said to be more than forty important 
manufacturing cities in southern New England that can trace their 
start to an early advantage in water power. Nearly all of them now 
use much more steam power than water power. 

The use of coal and steam power in manufacturing increased 
rapidly after 1850. The growth of railroads steadily increased the 
number of places which could get coal, and also made cheaper the 
movement of raw materials to places situated favorably with respect 
to supplies of coal. The advantage of large deposits of good coal has 
had much to do with the remarkable industrial development since 1850 
in the region extending from western Pennsylvania to Illinois. 

The use of other mineral fuels for industrial purposes also has located certain 
manufactures. Thus the discovery of natural gas in western Pennsylvania, Ohio, 
Indiana, and West Virginia attracted many industries because of the cheap and 



382 DISTRIBUTION OF INDUSTRIES 

excellent fuel offered. In many places the supply of natural gas failed after a 
few years, and as a result many factories were abandoned or moved; some of the 
larger ones continued to operate by bringing in coal. California is beginning to 
feel the benefit of the large supplies of cheap oil discovered there within the last 
few years. Formerly, the industrial development of the state was retarded by the 
fact that much fuel had to be imported at relatively heavy expense. 

As the supply of fuels diminishes, hydro-electric power will be 
used more and more in manufacturing (p. 289). But the ease of 
transmitting the power to considerable distances removes the need 
of locating the factory near the source of the water power (p. 288). 

Influence of nearness to market. The advantages of a nearby 
market, or of superior facilities for shipping goods to more distant 
markets, have been leading factors in determining the location of many 
industries. 

An example is afforded by the location of the leading refineries handling 
imported cane-sugar. Sugar is refined and molasses is manufactured to some 
extent in Louisiana, where cane is grown. But much cane-sugar is imported, 
and the largest refineries are in New York and Philadelphia, in part because 
of the heavy local consumption and the excellent means of distribution to out- 
side markets. Furthermore, by having the refineries at tidewater the cost of 
transporting the raw material is reduced. 

A more striking case is that of the manufacture of agricultural implements. 
The chief market for these things is in the leading farming sections. Many im- 
plements are very heavy and occupy much car- space, so that freight rates on them 
are high. For their manufacture, there is accordingly great advantage in a loca- 
tion near the chief market. As a result, there has been a steady westward migra- 
tion of the industry as the great grain districts have expanded in that direction 
(p. 361). In 1880, Ohio and New York were leaders in the industry; now, Illinois 
is far ahead of both combined, its output having increased threefold between 
1880 and 1910. 

Influence of supply of labor. The importance of a local sup- 
ply of labor in determining the location of manufactures varies great- 
ly. It depends in part on the character of the industry, being more 
important in the case of industries requiring skilled labor than in 
others. In general, it is much less important now than formerly, 
for it has become increasingly easy to attract laborers to any given 
point where other conditions are favorable. Doubtless, too, labor 
will be even more mobile in the future. 

In the past, manufacturing in parts of the South and in California has been 
retarded by lack of a satisfactory supply of labor. On the other hand, the leader- 
ship of New York City in the ready-made clothing industry is due in part to the 
presence of abundant cheap labor. The supremacy of New England in the manu- 
facture of cotton has been maintained of late years largely through the possession 
of expert workers. 



IMPORTANCE OF URBAN INDUSTRIES 383 

Other factors. In addition to the leading factors discussed 
above, there are various minor factors which may influence the 
location of manufacturing industries. Thus the advantage of an 
early start has located certain industries in places without superior 
natural advantages. In most cases this advantage is associated 
closely with the question of labor. 

The boot and shoe industry of Brockton, Lynn, and Haverhill, Massachusetts, 
illustrates the advantage of an early start. The industry was established in these 
places at an early date, and by enlisting the services of many of the people, a 
supply of skilled labor was developed with enough impetus to give first rank to 
the localities. Most of the shoe factories of these cities are run by steam power, 
developed from Pennsylvania coal, and most of the leather they use is tanned 
in other states. Clearly, their leadership rests on an insecure basis, and the 
business is growing fast in other cities having more fundamental advantages. 

In earlier years, industries frequently were established in particular places 
because of a supply of local capital, but now such cases are relatively few and 
unimportant. Broadly speaking, capital is perfectly mobile, and goes wherever 
other conditions are favorable. Climate may also be a direct factor in determin- 
ing the location of manufacturing industries, though its influence is offset easily 
by other considerations. Thus the climate of the northern states is more invigorat- 
ing than that of the southern states, and workingmen are likely to render more 
efficient service, on the average, in the former than in the latter. Yet because of 
other advantages, the manufacturing industries of the South are growing rapidly. 

Combined influence of various factors. While many indus- 
tries are located largely or wholly by one or two factors, the distri- 
bution of others is the result of the combined influence of most or 
all of the things mentioned above. Many industries, too, have been 
located without regard to the geographic and economic conditions 
involved, and not a few have failed for this reason. 

Further illustrations of the leading factors which influence the 
distribution of industries occur in the following pages, in connection 
with the discussion of the leading manufactures of the country. 

The leading manufacturing states and cities. New York, Penn- 
sylvania, Illinois, Massachusetts, and Ohio, in this order, are the 
five leading manufacturing states, while New York, Chicago, Phila- 
delphia, St. Louis, and Cleveland are the five most important manu- 
facturing cities. In 19 10, the combined value of the manufactured 
products of cities having a population of 10,000 or more was more 
than twice that of smaller cities and rural districts. The more rapid 
growth of urban as compared with rural population has been one of 
the most striking and significant things in connection with the popula- 
tion changes of recent years (p. 399). It has been due in large part 



3§4 



DISTRIBUTION OF INDUSTRIES 



to the rapid growth of urban industries. The factories in the territory- 
east of the Mississippi River and north of the Ohio and Potomac 
rivers employ about ^4 of all the industrial wage-earners (not workers 
on farms) of the country, and contribute about the same proportion 
of the total value of manufactured products. 

Leading Manufactures of the United States 
The Federal Census Bureau has divided the 339 classes of manu- 
factures that are carried on in the United States into 14 groups. 
These are shown in the accompanying table. 



MANUFACTURING INDUSTRIES OF THE UNITED 

{Ranked according to value of product in 1909) 



STATES 



Group 



Food and kindred products 

Iron and steel and their 
products 

Textiles 

Lumber and its manu- 
factures 

Chemicals and allied prod- 
ucts 

Metals and metal products, 
other than iron and steel 

Paper and printing 

Vehicles for land transpor- 
tation 

Leather and its finished 
products 

Liquors and beverages .... 

Clay, glass, and stone 
products 

Tobacco manufactures 

Shipbuilding 

Miscellaneous industries. . . 
United States 



Year 


Number of 
establish- 
ments 


Wage earners 
(average 
number) 


Value of products 


1909 
1899 


55,364 
41,247 


4H,575 
301,868 


$3,937,617,891 
2,199,203,442 


1909 
1899 


17,289 
14,080 


1,025,044 
744,o69 


3,163,126,293 
1,818,036,771 


1909 
1899 


21,695 
17,640 


1,437,258 
1,021,869 


3,054,708,084 
1,627,889,077 


1909 
1899 


48,533 
34,947 


907,514 
669,043 


1,582,522,263 
1,004,716,682 


1909 
1899 


11,745 
8,687 


237,988 
179,539 


1,430,901,954 
726,105,558 


1909 
1899 


8,750 

4,996 


248,785 
160,422 


1,238,251,401 
688,927,152 


1909 
1899 


34,828 
26,627 


415,990 
298,744 


1,179,285,247 
607,957,231 


1909 
1899 


8,248 
8,738 


507,3H 
3M,283 


999,326,577 
504,969,835 


1909 
1899 


5,728 
5,625 


309,766 
248,626 


99 2 ,7I3,322 
582,047,900 


1909 
1899 


7,347 
5,740 


77,827 
55,120 


674,3H,05i 
382,898,381 


1909 
1899 


16,168 
11,524 


342,827 
231,716 


531,736,831 
270,650,143 


1909 
1899 


15,822 
14,959 


166,810 
132,526 


416,695,104 
263,713,173 


1909 
1899 


i,353 
1,107 


40,506 
46,747 


73,36o,3i5 
74,532,277 


1909 
1899 


15,621 
n,597 


485,845 
308,191 


1,397,495,537 
655,279,079 


1909 
1899 


268,491 
207,514 


6,615,046 
4,712,763 


20,672,051,870 
11,406,926,701 



HISTORY OF MEAT-PACKING INDUSTRY 385 

Food and kindred products. The more important items in this 
group are slaughtering and meat-packing products; flour and grist 
mill products; butter, cheese, and condensed milk; canned and pre- 
served fruits, vegetables, and fish; and refined sugar (p. 382). 

The slaughtering and meat-packing industry tends to keep close 
to the great stock-raising areas (pp. 366-368), in order to avoid freight 
charges on waste material and to prevent the animals losing weight on 
the way to the slaughtering centers. The total value of the products 
of the industry in 1910 was $1,370,000,000. 

Grazing naturally precedes farming in the order of economic development (Why?) , 
and as the chief grazing area moved westward in front of the advancing agricultural 
zone, the slaughtering and packing industry followed. In early days, stock was 
driven from the pastures of the Piedmont Plateau to be killed at Philadelphia, 
Baltimore, and Charleston. The battle of Cowpens, in the Revolutionary War, 
was so called because fought about the pens of a Piedmont cattle ranch. Later, 
great numbers of cattle and hogs were driven to the seaboard from the settlements 
west of the Appalachians (p. 274). After the War of 1812, the pork-packing indus- 
try found its chief center in Cincinnati, where it remained until about i860 (p. 276). 
During this period, the business was carried on also at various other points on 
the Ohio canals and the Ohio, Mississippi, Illinois, Wabash, and other rivers. 
By 1861-1862, the center of the industry had moved from Cincinnati to Chicago, 
and the business had declined in many of the river towns. Greater economy in 
manufacture was possible in a small number of large establishments than in a large 
number of small ones, and Chicago, as the greatest railroad center, had unrivaled 
facilities for assembling the stock. It is also on the northern edge of the corn belt 
(Fig. 259; Why important?), and within easy reach of the great grazing lands. 
Chicago still leads in the industry, contributing nearly y$ of the total value of the 
products for the country, but the second and third centers are found on the Missouri 
River, at Kansas City and South Omaha, respectively. The most important 
thing in the recent history of this industry has been the more and more nearly com- 
plete use of the waste products of the slaughter houses. Among the things made 
from these products are soap, candles, glue, gelatine, glycerine, ammonia, knife- 
handles, and fertilizer. • 

The value of the flour and grist mill products of the United 
States has increased rapidly with the growth in the production of 
cereals, and in 1910 amounted to more than $880,000,000. Five- 
eighths of the value of the output of these mills is in wheat flour. Other 
important products are rye and buckwheat flour, corn meal, and 
feed for animals. All branches of the industry have expanded west- 
ward, following the westward movement of the centers of production 
of the great cereal crops (Fig. 261). Flour and grist mills are distribut- 
ed widely, for with the exception of a comparatively few large mills, 
they supply local demands only. Minnesota, New York, Kansas, 



386 DISTRIBUTION OF INDUSTRIES 

Ohio, and Illinois are the leading flour-producing states, and Minne- 
apolis is the leading city (p. 288). 

The manufacture of dairy products in factories is a modern 
development. Formerly, this work was done almost entirely on 
the farms. In 185 1, there was only one cheese factory in the United 
States; in 1905, there were more than 3,600. New York, Wisconsin, 
Iowa, Illinois, Minnesota, and Pennsylvania are the six leading states 
in the industry (p. 366). The value of factory-made butter, cheese, 
and condensed milk exceeded $270,000,000 in 1910. 

The canning and preserving of foods is a comparatively new 
industry in the United States, having little importance before 1850. 
Now, the total yearly value of canned foods, exclusive of meats, 
is about $160,000,000. The leading states in the industry are Cali- 
fornia, Maryland, and New York. The conditions which determine 
the distribution of the industry have been given (p. 379). 

Iron and steel and their products. This group of manufac- 
tures ranks second in value of product (p. 384). It comprises 37 
industries, the basic ones being the manufacture of iron and steel. 
Among the others are those producing structural iron work, rails, 
machinery, tools, hardware, tin plate (really sheets of iron coated 
with tin), and various small products. The iron and steel industry 
is carried on in some 27 states, but nearly 9/ IO of the total output 
comes from Pennsylvania, Ohio, Illinois, and Alabama. 

The successful use of hard coal as fuel gave the first great impulse to iron 
production, and located the iron industry in eastern Pennsylvania, with Phila- 
delphia the leading market. About the close of the Civil War, the center of the 
industry moved to Pittsburgh, where it still remains. A number of influences led 
to the change: (1) The hard coal of eastern Pennsylvania, because less abundant 
and in great demand for domestic use, cost more than the soft coal of the western 
part of the state. Furthermore, coke made from the latter was more efficient, 
ton for ton, than hard coal. (2) The Lake Superior ore was of high average grade, 
was mined easily, and could be brought to Lake Erie ports cheaply by lake. (3) 
The rapid development of the country west of the Appalachians helped to bring 
about the change. Although Pittsburgh did not become the center of the industry 
until after the Civil War, it had nail factories, foundries, and the like, before the 
beginning of the century. As indicated elsewhere (p. 282; Fig. 198), Lake Superior 
iron ore goes to Pennsylvania coal, rather than the reverse, because much more coal 
than ore is needed in the manufacture of steel, and because the ore, in being sent 
to Pittsburgh, is on the way to its final market. Various phases of the iron industry 
are carried on less extensively at other cities on or near the Great Lakes, especially 
at Chicago and Cleveland, where ore and coal can be brought together cheaply, 
and where market conditions are good. 

In the South, Birmingham, Alabama, is the leading center of the iron and 



THE TEXTILE INDUSTRIES 387 

steel industry. In smelting iron ore it is mixed with limestone and coke, and when 
the mixture is heated in the furnace, the metal iron is released from the ore, and is 
drawn out into molds. At Birmingham, iron ore, coal, and limestone are found 
close together. This fortunate combination (with the Southern market) has made 
Birmingham an important city, and a leading factor in the industrial growth of 
the southern states. 

Textile manufactures. The industries of this group furnish 
the materials for nearly all our clothing and for many household 
articles, such as rugs and carpets, draperies, and bedding. Vegetable 
and animal fibers constitute the raw materials used by the 44 textile 
industries. The principal industries of the group are based on cotton, 
wool, and silk. Various products are made also from flax, hemp, and 
jute. 

The textile mills of the United States consumed in 1910 about 2,500,000,000 
pounds of raw cotton, valued at more than $290,000,000. The value of the cotton 
manufactures was more than $620,000,000. Southern New England has led in 
the manufacture of cotton throughout the history of the industry in the United 
States, but now its leadership is threatened seriously by the South Atlantic states. 
New England has the advantage of a much earlier start in the industry, and of a 
better supply of labor (p. 382); but the southern mills are very much nearer the 
cotton fields. Both sections possess abundant water power. This is a minor factor 
in New England, but a very important one in the South. 

Woolen manufactures include worsted goods, suiting, blankets, carpets, felt 
goods, and wool hats. Much wool is imported for the mills, which consume more 
than 500,000,000 pounds annually. The leading manufacturing centers are in the 
Middle Atlantic and New England states. 

The silk mills of the United States are dependent entirely upon foreign coun- 
tries for raw material. Mulberry trees could be grown and silkworms reared in 
this country, but the industry requires much hand labor, and the cost of the latter 
in the United States prevents the production of raw silk as cheaply as it can be 
produced in southern Europe, Japan, and China. The leading silk-manufacturing 
states are New Jersey, Pennsylvania, New York, and Connecticut. 

Lumber and its manufactures. The logging camp and lumber 
mill furnish material for the 23 other branches of industry included 
in this group. The fundamental industries have been discussed 
(pp. 370-372). Among the products of the industries which use lum- 
ber are doors, blinds, sash, interior finish, boxes, matches, "wooden- 
ware," and furniture (p. 380). Great quantities of lumber are used 
also in building, and in certain industries included in other groups, 
such as shipbuilding and the manufacture of carriages and wagons. 
Lumber products are manufactured on a commercial scale in every 
state, in marked contrast with the concentration of certain of the 



388 DISTRIBUTION OF INDUSTRIES 

other greater industries, such as the manufacture of iron and steel 
and textiles. 

Chemicals and allied products. This group contains many 
manufactures which serve a wide variety of purposes. Among the 
products are paints and varnishes, dyestuffs, bleaching materials, 
medicines, druggists' preparations, baking powder, glue, soap, ink, 
various oils, explosives, and fertilizers. Naturally, such diverse com- 
modities are manufactured in many different places, but more than 
half the products of the group as a whole come from Pennsylvania, 
New York, New Jersey, Ohio, and Illinois. 

Metals and metal products other than iron and steel. Many 
things are made of gold, silver, copper, lead, and zinc (pp. 181-182), 
such as jewelry, watches, clocks, silverware, brassware, and pins. 
Many of the 34 classes of industry belonging to this group are carried 
on extensively in the northeastern states, especially southern New 
England. The chief advantages enjoyed by this section in these 
industries are (1) an early start, and (2) the services of skilled work- 
ers, more numerous there than elsewhere during the early develop- 
ment of these industries. 

Paper and printing. Printing and publishing are the most 
important and most widely distributed industries of this group, 
which includes also the manufacture of wood-pulp, paper of all 
kinds, paper bags and boxes, etc. 

The principal centers of the wood-pulp industry have been noted (p. 380). 
The output of paper boxes has increased rapidly during recent years ; largely be- 
cause of the increasing cost of wood, many things are now put up in paper boxes 
which formerly were packed in wooden boxes. The annual per capita value of the 
output in the printing and publishing business is more than ten times greater 
than it was in 1850. This significant change reflects in part the progress made in 
education, the reduced cost of reading matter, and the greater facilities for its 
distribution, such as rural free delivery. In 1905, the value of the products of 
printing and publishing in six states — New York, Illinois, Pennsylvania, Massa- 
chusetts, Ohio, and Missouri — amounted to ^3 that for the entire country. 

Vehicles for land transportation. The operations of the repair 
shops of steam railroad companies, the manufacture of carriages 
and wagons, and the manufacture of steam railroad cars are the 
most important of the 11 industries comprising this group. In 
recent years the output of bicycles has declined rapidly, while that 
of automobiles and motorcycles has increased enormously. 

The value of the automobiles made in 1900 was less than $5,000,000; in 1910, 
about $165,000,000. In 1905, automobiles were manufactured in 17 states, with 



LEATHER PRODUCTS AND LIQUORS 389 

Michigan, Ohio, New York, and Connecticut leading. The value of those made 
in Detroit is more than y^ of the total for the industry. The leadership of 
Detroit appears to be due to the impetus resulting from the success of the first 
factories established, rather than to superior natural advantages. 

Leather and its finished products. The basic industry in this 
group is tanning, while the dependent industries include the manu- 
facture of leather products of all kinds. Of the latter, the boot and 
shoe industry is most important, but large quantities of leather 
are used in making harnesses, saddles, trunks, bags, furniture, gloves, 
mittens, and belting, in binding books, and in other ways. For 
many years Massachusetts has been the leading shoe-manufacturing 
state (p. 383), but the industry is growing rapidly at various points 
in the middle states. 

In the past, the tanning industry has depended chiefly on local supplies of 
tannic acid, obtained usually from the bark of oak or hemlock, and as the supply 
of bark failed in one area, the industry developed in another. The business is now 
important in Pennsylvania, Michigan, and Wisconsin. Until recently, the industry 
was attended by an enormous waste of timber; trees were felled by thousands, 
from which only the bark was taken for the tanneries, the logs being left to rot in 
the woods. 

Liquors and beverages. The value of these products increased 
more than % between 1900 and 1910, amounting to more than $590,- 
000,000 in the latter year. Illinois leads the states in making dis- 
tilled liquors, while Indiana, Ohio, and Kentucky follow in the order 
named. New York, Pennsylvania, Wisconsin, Missouri, and Illinois 
are the leading states in the production of malt liquors. California, 
New York, and Ohio lead in wine-making. 

Peoria, Illinois, ranks first among American cities in the manufacture of 
distilled liquors. It attained leadership in the liquor industry largely because of 
(1) its central location in the corn belt of the state; (2) its transportation facilities, 
which enable it to collect at low freight rates the surplus grain of the surrounding 
area; and (3) an abundant supply of cheap coal from nearby mines. The manu- 
factured product, owing to its relatively small bulk and large value, can bear the 
cost of transportation to distant markets. Nearness to the grain supply has also 
been an important factor in the manufacture of malt liquor in Milwaukee, Chicago, 
St. Louis, Cincinnati, and St. Paul. 

Clay, glass, and stone products. Some of the industries of 
this group have been noted sufficiently in earlier connections (pp. 
175-176, 266). Clay products are used most in the building trades, 
and their consumption is increasing rapidly. Ohio, Pennsylvania, 
New Jersey, Illinois, and New York lead in clay products. Pennsyl- 
vania, Indiana, and Ohio lead in the manufacture of glass. 



3QO DISTRIBUTION OF INDUSTRIES 

Deposits of quartz sand, the only raw material which enters into all kinds of 
glass, are widespread, but the making of glass on a large scale is fairly well localized 
because of the need of satisfactory fuel for the work. With good fuel, a skillful 
glass-maker can make fairly good glass from inferior material, but with poor fuel 
he cannot make good glass with the best materials. Gas is the ideal fuel in glass- 
making, because it is cleanest, and gives intense, uniform heat under perfect 
control. The leading states in the industry attained that position largely because 
of their supplies of natural gas. 

Tobacco products. These include cigars, cigarettes, chewing 
and smoking tobacco, and snuff. The value of the products increased 
from $31,000,000 in i860 to $416, 000,000 in 1910. 

The manufacture of cigars is distributed widely, Pennsylvania, New York, and 
Ohio leading. More than 4/5 of the total output of cigarettes are made in New 
York and Virginia. Missouri, North Carolina, Kentucky, and Virginia lead in 
the production of chewing and smoking tobacco. 

Shipbuilding. Since 1850, the value of the products of this 
industry has increased nearly fourfold and the capital invested 
twenty-one fold. The latter fact means that, as iron and steel steam- 
ships replaced wooden sailing vessels, much more capital was required 
than when ships were built of wood only. The need of greater capital 
helped to bring about the concentration of shipbuilding in large 
establishments, with the result that there were only about half as 
many establishments in 1905 as in 1880. New York, Pennsylvania, 
Virginia, New Jersey, and Massachusetts are the leading shipbuilding 
states on the Atlantic coast; Ohio and Michigan lead on the Great 
Lakes ; and California and Washington on the Pacific coast. 

The rapid growth in recent years of the shipbuilding industry on the Great 
Lakes has been due to the demand created by the enormous increase in the com- 
merce of the lakes (pp. 270, 282). At the same time, of course, the development of 
shipbuilding has favored the continued growth of lake transportation. The ship- 
yards at West Bay City, Michigan, and West Superior, Wisconsin, are outgrowths 
of the wooden shipbuilding industry. Those at or near Buffalo, Lorain, Cleveland, 
Toledo, Detroit, and South Chicago are located conveniently with reference to 
the great steel mills. 

Miscellaneous industries. There are 65 industries of varying 
importance carried on in the United States which cannot be classed 
properly with any of the other groups. The combined value of their 
products in 1910 was more than $1,400,000,000. Among the indus- 
tries of the group whose products are of greater value are the manu- 
facture of agricultural implements (p. 382); ammunition; brooms 
and brushes; buttons; coke (p. 386); electrical machinery, apparatus, 



! 



QUESTIONS 391 

and supplies; fur goods; ice; mattresses and spring-beds; musical 
instruments; photographic materials and apparatus; and rubber and 
elastic goods. 

Questions 

1. (1) Explain the fact that the shores of Chesapeake Bay, Long Island, and 
Lake Michigan (east shore) were among the first sections to grow vegetables on 
a large scale for city markets. (2) Why is the business more important on the 
east shore of Lake Michigan than on the west shore? 

2. Formerly strawberries were grown extensively in a few places only, as in 
parts of Maryland, New York, Ohio, and western Michigan. Now they are grown 
on a large scale in Florida, Tennessee, Arkansas, Missouri, and other states. (1) 
Explain the relatively early development of the business in the first-mentioned 
states. (2) What permitted its later development in the other states? 

3. It is estimated that the forests of the United States (Fig. 271) contain about 
the following percentages of their original stand of timber: Northern Forest, 
30 per cent; Hardwood Forest, 21 per cent; Southern Forest, 50 per cent; Rocky 
Mountain Forest, 75 per cent; Pacific Forest, 79 per cent. Why the differences? 

4. What advantages have made New Jersey a great manufacturing state 
(6th in 1910), in spite of the fact that it has small fuel and water-power resources, 
and produces relatively little of the raw material used by its factories? 

5. Explain the fact that in Nebraska most of the manufacturing is done in 
the eastern part of the state (more than 4 /s of it in two counties) , while in Iowa 
it is distributed rather evenly throughout the state. 

6. Among the leading manufactures of Chicago are meat products, men's 
clothing, foundry and machine shop products, iron and steel, the products of 
printing and publishing houses, and railroad cars. What advantages has Chicago 
for carrying on each of these industries? 

7. Compare and contrast the general advantages for manufacturing of (1) 
Massachusetts and Texas, and (2) Utah and Ohio. 

8. Flour and sugar are household necessities. (1) Explain why the former 
is made in thousands of mills throughout the country, and the latter at compara- 
tively few points. (2) Will the situation with regard to sugar change in the future? 
Why? 

9. Why does West Virginia rank low (29th) as a manufacturing state, although 
it mines much coal (second coal-producing state in 1910)? 

10. Explain the fact that the section east of the Mississippi River and north 
of the Ohio and Potomac rivers contributes about $i of the total value of man- 
ufactured products for the United States. 



CHAPTER XXI 
DISTRIBUTION OF POPULATION; DEVELOPMENT OF CITIES 

Factors Affecting Density 

As we have seen, the distribution and density of population are 
influenced by many factors — such as topography, climate, soil, 
natural resources, transportation facilities, and the occupations of the 
people. The influence of these factors may be reviewed by consider- 
ing briefly the expansion and present distribution of population in 
the United States. 

Fig. 276 shows the distribution of population in 1790, when the 
first census was taken. Nearly all the people, emigrants from 
Europe, were still east of the Appalachian Mountains. This was 
due largely to the difficulty of crossing the mountain barrier, the 
privations, dangers, and difficulties of life in the Interior, and the 
desirability of being near the Atlantic Ocean or some navigable river 
flowing into it, for purposes of trade. Furthermore, the lands east 
of the mountains and along the Great Appalachian Valley had been 
sufficient for the needs of the settlers until a few years before (about 
1775)- 

In New England, the population was densest toward the south and south- 
east. This is explained by the colder climate at the north; the rough uplands 
there, infertile in many places; the fact that few of the rivers served as good high- 
ways far into the interior (Why?); and the importance of sea-interests (fishing, 
shipbuilding, the carrying trade) in New England life. The influence of the 
Connecticut Valley and the Champlain lowland on the distribution of the frontier 
population is interesting. In New York , most of the people were in or near the Hudson 
and Mohawk valleys, which had fertile soils in many places, and afforded easy com- 
munication with New York City. The Adirondacks and Catskills were almost unin- 
habited. The sandy, forested coastal plain of southeastern New Jersey had a sparse 
population, while a strip of denser settlement extended across the state between 
Philadelphia and New York City. (Why? Compare with Figs. 278 and 281.) 
In the Carolinas the Piedmont Plateau, with its relatively small farms, had a 
denser population than parts of the Coastal Plain, with its big plantations. The 
influence of the Great Appalachian Valley is shown by the settled strip which 
extended southwest from Virginia. The settled area in southwestern Pennsyl- 

392 



THE UNITED STATES IN 1790 



393 




Under 2 inhab. to the Sq. Mile [ 
2 

6-18 
18-45 
45-90 
90 and over 



83" 8.r 



Fig. 276. Map showing distribution of population in the United States in 1790. 



394 



DISTRIBUTION OF POPULATION 



vania reflects, in part, the attractions of the Monongahela Valley and some of 
its tributaries. The large area of settlement in north-central Kentucky was the 
famous "Blue Grass Region." Here were, rich soils, salt springs (p. 183), and 
navigable streams. The settlers of central Tennessee were also in a region of fertile 
soils, and used the Cumberland River as a highway. . The rough plateau lands of 
eastern Tennessee, Kentucky, and West Virginia had few settlers, or none at all. 

After 1790 population spread rapidly toward the west (Fig. 277), 
especially along such highways as the Ohio River and (later) the 
Great Lakes (p. 281). The population map for 1820 (Fig. 278) 
shows strikingly the influence of geographic features. The Adiron- 
dack Mountains and the less accessible parts of the Appalachian 
Mountains and the Alleghany Plateau remained uninhabited wil- 




Fig. 277. Map showing the center of population in the United States at each 
census, 1790 to 1910. 

dernesses. On the other hand, most of the fertile lowlands favorably 
situated and available for settlement had been occupied. The 
most striking feature of the western frontier was the control of 
settlement by the larger rivers, which were the chief highways of the 
time (pp. 274-276). Each one (the Red, Arkansas, Missouri, Missis- 
sippi, and others) was bordered for some distance by a narrow settled 
area, while, for the most part, the tracts between were still unoccu- 
pied. The influence of routes from the East is illustrated by the 
belt of settlement extending from western New York around the 
southern shore of Lake Erie to Lake St. Clair. The presence of 
Indians explains some of the blank areas on the map within the 
generally settled region, as in Georgia, Alabama, central and northern 
Mississippi, and western Tennessee. After the removal of the 
Indians, these areas were settled quickly. 

The unsettled condition of northwestern Ohio was due partly to the "Great 
Black Swamp." The lower part of the Mississippi delta and some of the lands 
along the Gulf coast also were unoccupied because swampy. For some years, 
settlers avoided the prairies of the northern Interior. They were thought infertile 
(P- I 73)> timber must be had for buildings, fences, and fuel; they did not afford 



DISTRIBUTION OF PEOPLE IN 1820 



395 



43-0— 

41 



9,5 91 89 





wmmmf 




NOTE 
Center of Population 
78°33'W.39°5.7'N. 

Under 2 inhab. to the Sq. Mile \~. 

« ' " " I - I 

6-18 « « » « "T 1 

«■« '• " EZ3 

45 : 90 " «' 
90 and over" 



:z~ 



Fig. 278. Map showing distribution of population in the United States in 1820. 



396 



DISTRIBUTION OF POPULATION 




THE WEST IN 1880 397 

enough running water for stock or mills; there was little protection from the 
bitter winds of winter; and the farmers did not know how to "break" and work 
the tough prairie sod. The gradual conquest of the prairies is one of the most 
interesting phases of the settlement of the region. The dense forests in the north- 
ern Lake region helped for years to keep farmers away from large areas. 

The appearance of the railroad introduced a new and powerful 
factor in the expansion of population. The first American railroad 
was built in Massachusetts in 1826. By the early 1850 's, railroads 
had been built across the Appalachian Mountains from the leading 
seaports of the Northeast. In 1853 Chicago was connected by rail 
with New York City. The Mississippi River was reached shortly 
after, and in 1869 the first railroad was completed to the Pacific. 
The railroads opened up vast areas for settlement which had not been 
available before. This was particularly true of large areas west of 
the Mississippi, whose settlement and development, in the absence 
of navigable waterways, had to await the railroad. Fig. 279 shows 
the present railroad web. 

By 1880, many parts of the West were settled (Fig. 280). Fertile 
soils had favored farming along the bases of some of the mountains 
and in many valleys, the discovery of mineral deposits had attracted 
thousands of prospectors and miners to various places, and the graz- 
ing industry supported a sparse population over wide areas. 

The settlements in the Black Hills (Fig. 280) were the result of the recent 
discovery there of gold. Most of the settlers in central and western Montana 
were farmers, located chiefly in the valleys of the larger streams. Besides the 
farmers, there were some miners. In Colorado there were farmers (1) along the 
east base of the Rocky Mountains, where, at many points, irrigation was possible, 
and (2) in some of the mountain valleys. In addition, a large mining population 
had been attracted by the discovery, a few years before, of rich deposits of gold, 
silver, and lead in the Leadville district (p. 315). In New Mexico, the Rio Grande, 
Rio Pecos, and upper Canadian valleys had drawn many settlers. In Utah, the 
agricultural settlements of the Mormons extended along the base of the Wasatch 
Mountains, where there were fertile and irrigable soils (p. 291). The principal 
agricultural settlements in Nevada were in the Humboldt Valley and along the 
Central Pacific Railroad. The other settlements of the state depended chiefly 
on mining. In California, the commercial advantages of San Francisco Bay had 
attracted many people, and some of the gold-producing districts were well settled. 
The great central valley and the more inviting valleys of the Coast Range were 
occupied by farmers. 

The lowlands west of the Cascade Mountains in Oregon and Washington were 
occupied for the most part, while in the drier regions east of those mountains most 
of the settlements were near the Columbia River and its tributaries. The remain- 
ing population of the West was scattered widely at military posts, mining camps, 
and on cattle ranches. 



398 



DISTRIBUTION OF POPULATION 




Fig. 280. Map showing distribution of population in the West in 1880. 



DISTRIBUTION OF PEOPLE IN 1900 399 

The population map for 1900 (Fig. 281) will be understood readily 
in the light of the preceding discussion, and only its larger features 
need be noted here. The population of the eastern half of the 
country was seven times as great as that of the western half. The 
relatively sparse population of the western half was due chiefly to 
prevailing aridity and the great extent of mountains and plateaus. 
Furthermore, many of the settled areas were occupied only recently. 
The relation of precipitation to population is suggested by the fact 
that only about V30 of the people were in regions where precipitation 
is less than 20 inches. Similarly, the relation of altitude to popula- 
tion is shown by the fact that more than 95 per cent of the population 
lived at elevations of less than 2,000 feet. Since 1900, the population 
of many parts of the West has grown rapidly because of the develop- 
ment of irrigation, dry-farming, and mining, and the growth of com- 
mercial and industrial centers. The greatest densities (Fig. 281) are 
found in the northeastern quarter of the country. This region in- 
cludes much of the glaciated area, with its highly productive soils; is 
unrivaled in its transportation facilities (Fig. 279); possesses vast 
resources in timber, in iron, coal, copper, and other useful minerals; 
and contains most of the great commercial and industrial centers 
of the country. 

Cities 

Cities have increased rapidly in the United States, both in num- 
ber and size. In 1850, 12.5 per cent of the total population of the 
country lived in the 85 cities which had 8,000 or more people each; 
by 1900 the percentage of the population living in such cities had 
increased to 32.4, and the number of such cities to 517. Nearly half 
of the people of the country now live in villages and cities of more 
than 2,500 inhabitants. The increasing proportion of the population 
in cities has been due chiefly to the growth of urban commerce and 
industries (p. 383). The region with most cities is east of the 
Missouri River, and north of the Ohio and Potomac rivers. Here 
are 35 of the 50 cities which, in 1910, had a population greater than 
100,000. 

The leading types of cities are (1) commercial cities, (2) manu- 
facturing cities, (3) mining cities, (4) political centers, and (5) health 
or pleasure resorts. Most large cities are both commercial and 
industrial centers, while some belong also in varying degree to one 
or more of the other classes. 



4oo 



DISTRIBUTION OF POPULATION 




ON , 



CO I 

<u 
■M 
ed 

-a | 

CD > 



•3 ! 



CO 

3 






THE RISE OF COMMERCIAL CITIES 401 

Commercial cities. Cities dependent chiefly on commerce 
grow up (1) where conditions favor the collection and distribution of 
commodities on a large scale, or (2) on important lines of communica- 
tion at points where the mode of transportation is changed. Such 
places are (1) seaports, (2) river ports, (3) lake ports, and (4) railroad 
centers. 

(1) The growth of seaport cities is influenced mainly by (a) 
their position in relation to great trade routes; (b) the size, resources, 
population, and accessibility of their tributary areas {hinterlands)) 
and (c) the character of their harbors. The ideal harbor is large 
enough to contain many vessels, deep enough to admit the largest 
ships, protected from storms, free from ice, connected with the open 
sea by a deep channel, and has shores of such a kind as to facilitate 
the building of docks and the handling of freight (p. 350). Com- 
mercial cities are likely to grow up at or near the mouths of navigable 
rivers, for the latter serve as highways into the interior, and in many 
cases afford good harbors. When the lower courses of rivers have deep 
channels, such cities may be some distance upstream, nearer the 
heart of the country. Thus Montreal, more than 800 miles inland, 
is, in effect, a seaport. 

San Francisco has a fine harbor (Fig. 242), but trade with countries across 
the Pacific has been relatively unimportant; high mountains separate it from the 
interior; and to the east of these mountains stretch broad deserts with sparse 
populations. For years Boston, Philadelphia, and Baltimore, having good harbors 
and local hinterlands of importance, rivaled New York City in commercial im- 
portance. But the Hudson-Mohawk depression gave New York the best connec- 
tions with the interior, and the opening of the Erie Canal (p. 286) added the Great 
Lakes Region to its hinterland, enabling it to leave the others behind. 

(2) Since water transportation preceded railway transportation, 
most early inland cities are located at strategic points on navigable 
waterways, (a) At the head of river navigation goods are trans- 
ferred from water to land, or vice versa, for further distribution, 
and hence commercial towns develop. Thus Haverhill grew up at 
the head of navigation on the Merrimac, Hartford on the Connecti- 
cut, Albany on the Hudson, Augusta on the Savannah, and St. Paul 
on the Mississippi, (b) River cities are found also at the junctions 
of large rivers, for such places are focal points for trade. Here 
traffic coming upstream is divided, a part going up each stream, 
while in many cases freight descending the tributary streams is 
transferred to boats operating on the main river. Pittsburgh 



402 DISTRIBUTION OF POPULATION 

(p. 276), Cairo, St. Louis (p. 277), and Vicksburg are examples of places 
whose earlier growth, at least, was aided by their position near the 
junction of important streams, (c) A decided change in the direc- 
tion of a river 's course means a division of traffic and a change in the 
mode of carriage (Why?). Cincinnati (p. 276), Nashville, and 
Kansas City benefited from their positions on great bends of rivers. 
Kalamazoo, Michigan, and South Bend, Indiana, are types of many 
smaller places situated similarly, (d) Falls or rapids may give rise 
to a commercial city, for river freight must be unloaded, carried 
around the obstruction, and either reloaded or forwarded by land. 
The falls (rapids) of the Ohio made Louisville, those of St. Mary's 
River gave rise to Sault Ste. Marie, and the growth of Buffalo was 
aided by the falls and rapids of the Niagara. 

(3) All the more important cities ranged along the Great Lakes 
started as commercial towns — as centers of exchange and trans- 
fer — and their commercial activities still dominate. As noted 
elsewhere (p. 279), their exact location was determined in most 
cases by natural lines of communication leading from the shores of 
the lakes. 

Chicago became the greatest lake port because of its superior geographic 
advantages. (1) It is near the head of Lake Michigan, which extends farther than 
the other lakes into the heart of the country. (2) It is located more centrally than 
its rivals with reference to the richer areas of glacial soil and the areas leading in 
the production of corn (Fig. 259), wheat (Fig. 260), swine (Fig. 269), and cattle 
(Fig. 267). (3) All land traffic from the Northwest to the eastern part of the 
country must pass around Lake Michigan, and is therefore tributary to Chicago. 
The latter is accessible also by land from the south and east, from which directions 
many railroads have been built to Chicago to meet the traffic of the West and 
Northwest. Because of its strategic position, Chicago is the greatest railroad 
center in the world (Fig. 279). 

The importance of water transportation to the growth of the 
leading cities of the country is shown by the fact that of the 28 
cities having in 1910 a population of more than 200,000, 23 are on 
navigable waters. Of the 23, 10 are seaports, 7 are on the Mississippi 
System, and 5 are on the Great Lakes. 

(4) All the important seaports, river ports, and lake ports of the 
United States are also more or less important as railroad centers. There 
are also a number of large cities without water transportation, like In- 
dianapolis, which now owe their commercial importance largely or 
wholly to the fact that they are at the junction of several railroad 
lines. The greater cities of the United States had become important 



INDUSTRIAL AND MINING CITIES 403 

because of their natural advantages, before the appearance of rail- 
roads. Railroads were built to them to share in existing trade, which 
they later helped to increase. On the other hand, the extension of 
railroads throughout the country caused a multitude of small cities 
and villages to spring up on sites without natural advantages. Such 
places serve as collecting and distributing points for the surrounding 
country, and, if railway junctions, they derive more or less benefit 
from the resulting exchange and transfer of traffic. 

While the more important conditions which give rise to com- 
mercial centers have been mentioned, villages and cities may grow 
up at critical points on lines of communication for reasons not men- 
tioned above. Thus a ford or ferry on a river may locate a town. 
Harrisburg, Pennsylvania, developed from Harris' Ferry, where a 
land route toward the west crossed the Susquehanna River ; Zanesville, 
Lancaster, and Chillicothe, Ohio, grew up where an important early 
road (Zane's Trace) crossed the Muskingum, Hocking, and Scioto 
rivers. Again, a mountain pass upon which trade routes focus may 
give rise to a city. Cumberland, Maryland, has grown up in front 
of Wills Creek Water-Gap, important since the colonial period 
(p. 232). The growth of Denver has been stimulated by its relation 
to several of the passes in the Rocky Mountains. 

Manufacturing cities. Most large commercial cities are im- 
portant also as manufacturing centers (p. 383), for their transportation 
facilities make it easy to get raw materials together and to ship out 
the manufactured products. Labor, too, is abundant. New York, 
the commercial metropolis of the country, leads also in manufacturing; 
Chicago, the leading inland commercial city, is the second industrial 
center; and Philadelphia, the fourth commercial center, is third in 
industry. On the other hand, all industrial cities are necessarily, 
in varying degree, trade centers. In most cities, therefore, commercial 
and industrial activities are united in varying proportions determined 
largely by geographic conditions. The factors which control the 
distribution of manufacturing industries (pp. 379-383) control also 
the location of the cities to which those industries may give rise. 
Most distinctly industrial cities are located in response to (1) power 
resources, like many of the New England cities (p. 381), or (2) raw 
materials, like Birmingham, Alabama. 

Mining cities. Many villages and cities, especially in the 
West, have developed from camps about mines. As the mining 
industry in a given locality grew, tents gave place to buildings of 



4 o 4 DISTRIBUTION OF POPULATION 

wood and brick, business and professional men appeared to supply 
the needs of the miners, and busy settlements resulted, which in 
many cases became cities in a few years. Scran ton (Pennsylvania), 
Joplin (Missouri), Deadwood (South Dakota), Cripple Creek (Colo- 
rado), Butte (Montana), and Placerville (California) are types of a 
large number of cities and towns which have grown up solely because 
of the wealth of adjacent mines. 

Many cities at which there are no mines depend largely on the 
mining industry. Thus Pueblo (Colorado) and Anaconda (Mon- 
tana) were founded chiefly for extracting metals from ores. Sacra- 
mento and Denver first became important as outfitting and supply 
stations for nearby mines. Indeed, there are few cities in the far 
West which have not been influenced by the mining industry. 

Political centers. Few cities are merely political centers, 
for even though founded as such, their growth is almost certain to 
attract commercial, if not industrial, enterprises. Washington, 
D. C, is a striking exception. In locating state capitals, acces- 
sibility for the majority of the people has been a leading considera- 
tion. In states having a fairly uniform distribution of population 
and equal facilities for travel, the capital tends toward the geographic 
center. Thus the capital of Illinois shifted from Kaskaskia to Van- 
dalia, and later to Springfield; that of Tennessee from Knoxville to 
Nashville; and that of Pennsylvania from Philadelphia to Harrisburg. 
The centrally located capitals of Ohio, Indiana, Iowa, Missouri, and 
South Dakota illustrate the same principle. On the other hand, where 
the mass of the population is in one section of the state, the capital 
is likely to be located there. Thus Boston, Albany, Lincoln, and 
Topeka, though far from the geographic centers of their respective 
states, are not far from the centers of population in each case. The 
question of accessibility was considered, among others, in choosing 
the site for the national capital, but with the growth of the West it 
has come to have a marginal location. 

Health and pleasure resorts. The leading cities of this type 
have been stimulated in their growth by geographic conditions which 
make them attractive to the tourist or beneficial to the invalid; 
most of them are ocean, mountain, or mineral spring resorts. The 
attraction of the ocean resorts lies partly in their facilities for boat- 
ing and bathing, but chiefly in the occurrence of the cool sea-breeze 
(p. 74) in the hot days of summer, and in the tempering effects of 
winds from the sea in winter. Newport and Atlantic City are exam- 



LOCATION OF COLONIAL CITIES 405 

pies. Asheville (North Carolina) and Colorado Springs are among 
the best-known mountain resorts (pp. 131,317) of the United States, 
and Hot Springs, Arkansas, is the most prominent health resort 
created by " medicinal" springs (p. 211). Los Angeles and several 
neighboring places in southern California have become important 
resorts chiefly for climatic reasons. 

Location of early cities. At one time people were gathered 
in villages and cities chiefly because of the necessity for defense. 
For this reason many old cities are located in places affording pro- 
tection, as on hills and islands. Considerations of defense as well 
as of trade located many of the towns founded in this country during 
the colonial period. 

The site of Boston was chosen because of (1) its strength for defense, (2) its 
harbor, and (3) a supply of good water. Boston peninsula was connected with 
the mainland by a narrow isthmus, so low that for years it was under water at high 
tide if a strong wind blew off the bay. This favored defense toward the land. The 
harbor is roomy, deep, farther inland than any other north of Cape Cod, and is 
located centrally on the coast of Massachusetts. This favored trade, and helped 
to make Boston the leading town of the colony. New York was founded on 
Manhattan Island for safety and in the expectation that the Hudson River would, 
as it did, give it command of the trade of a large district. Quebec was founded 
to guard the St. Lawrence highway and to command the fur trade of the Interior. 
The river is much narrower there than at any point farther downstream (Why 
advantageous?); the inland location was expected to afford security from European 
enemies; and the "Heights of Quebec" furnished an ideal site for a fortress. 
Montreal was laid out on a hilly island in the St. Lawrence River, opposite the 
mouth of the Ottawa River. Thus it was reasonably safe from unexpected attack, 
and able to draw upon the trade of both valleys. 



Questions 

1. Discuss the leading occupations of the United States as factors affecting 
density of population. 

2. Why are there more important cities in the United States on the Atlantic 
coast than on the Pacific coast? 

3. Compare and contrast the commercial advantages of the seaports of south- 
eastern and northeastern United States. 

4. Why are there fewer cities on the Great Lakes in Canada than in the United 
States? 

5. Give examples, not mentioned in the text, of cities which have profited 
from their positions (i) on rivers at the head of navigation, (2) at the junctions of 
important rivers. 

6. Lexington was for years the largest community in Kentucky. Now the pop- 
ulation of Louisville is more than six times that of Lexington. Explain the change. 



4 o6 DISTRIBUTION OF POPULATION 

7. Why has Chicago derived greater commercial advantages from its location 
near the head of Lake Michigan, than Duluth has from its position near the head 
of Lake Superior? 

8. Why are Vio of the cities in the United States having in 19 10 a population 
of more than 100,000 situated east of the Missouri River and north of the Ohio? 

9. (1) Explain the relatively small population (1900) of (a) southern Florida 
and (b) northern Wisconsin and northern Michigan, as shown by Fig. 281. 

(2) Explain the distribution of population in (a) Montana, (b) the belt through 
southeastern Idaho and Utah, and (c) Xew Mexico. 

(3) Account for the areas of relatively dense and of relatively sparse population 
in California. 

(4) Cite illustrations (not involved in preceding questions) from the map. 
showing the influence on the distribution of population of (a) topography, (b) 
means of communication, and (c) natural resources. 

10. (1) Why is the railroad web (Fig. 279) thickest in the northeastern quarter 
of the country? 

(2) Account for the thinness of the railroad net in northern Xew England, 
northern New York, and the northern Lake Region. 

(3) Why is the dominant direction of railroads east-west in the Great Plains? 

(4) Why the relatively small railroad mileage of the western half of the country? 

(5) Explain the distribution of railroads in California. 



INDEX 



Abrasion by sand, 201 

Africa, area and population in tem- 
perate zone, 113; area and population 
in tropics, 98; general features of, 25; 
rivers of, 25, 269; trade with U. S., 
140, 141 

Agricultural implements, manufacture 
of, 382 

Agriculture, on alluvial fans, 236; in 
equatorial forests, '338; in irrigated 
lands, 297, 298; leadership of U. S. 
in, 359; in oases, 334; in mountains, 
311; and rainfall, 59, 76, 80, 119, 128, 
129, 291; in semi-arid regions, 327; in 
tropical grass lands, 104; in the 
United States, 357-370 

Air. See Atmosphere 

Alaska, agriculture in, 121, 137; cli- 
mate of, 79, 120, 136; coast of, 343; 
fisheries of, 376; glaciers of, 249, 250, 
251; gold mining in, 3 78 ; precipitation 
in, 79 

Aleutian Islands, 194 

Alfalfa, 30, 297, 363 

Alluvial cones and fans, 235, 236 

Alluvial plains, 237 

Alluvial terraces, 243 

Alluvium, 165 

Alps Mountains, 307, 317; glaciers of, 
250; life on sunny vs. shady slopes, 
44; stock-raising in, 314; zones of 
vegetation in, 313 

Altitude and climate, 109, 130 

Altitude and pressure, 66, in 

Altitude and temperature, 44, 52, 109, 
130 

Aluminum, 182-183, 377 

Amazon River, 104, 271, 345, 351 

American waterways, 271-287; im- 
provement of, 287 

Andes Mountains, 307, 320; as climatic 
barrier, 77, 105, 119 

Animal life, of Antarctic region, 136; of 
Arctic region, 137, 336; in caverns, 
212; in deserts, 107, 331; in the sea, 



Animal life — continued 

156-158; and soil formation, 164; in 
tropical forests, 338. See Life 

Animal products, 366-370 

Antarctic circle, 15, 133 

Antarctic region, climate of, 135; life of, 
135-136 

Antarctica, snow and ice of, 251 

Anthracite coal, 315, 377, 386 

Anticyclones, 83, 85, 89, 90, 93 

Aphelion, 7 

Appalachian Mountains, and early dis- 
tribution of population, 392, 394; and 
early western settlements, 274; forest 
reserve in, 173, 317; in history, 308; 
inhabitants of southern, 310; soils of, 
173; structure of, 305 

Apples, 365 

Arabia, desert of, 331, 333, 334 

Arctic circle, 15, 133 

Arctic regions, climate of, 136; ice of, 
136; life in, 137-138, 336 

Argentina, 122, 327 

Arid climate in temperate zones, 123 

Arid regions of the U. S., 79, 126 

Arid plains, life in, 330-336 

Artesian wells, 209, 302; in oases, 

334 

Asia, area and population in tropics, 98; 
caravan trade in, 335; climatic 
changes in, 79; general features of, 24; 
monsoons of, 75, 108-109; rivers of, 
269; trade with U. S.,.140, 141 

Asiatic cholera, 109 

Asteroids, 4 

Atlantic City, 404 

Atmosphere, circulation of, 72-74; com- 
position of, 28-29; density of, 27; 
functions of, 27; heating of, 39; 
height of, 28; impurities of, 29, 31, 32; 
relation to rest of earth, 27; tempera- 
ture of, 34; weight of, 27, 66; work of, 
204 

Atmospheric pressure, and altitude, 66, 
.hi; distribution of, 67 



4Q7 



408 



INDEX 



Australia, area and population in tem- 
perate zone, 113; area and population 
in tropics, 98; climate of, 105, 106, 
109, 326; droughts in, 80, 130; general 
features of, 24; grazing in, 327; Great 
Barrier Reef of, 159, 354; population 
of, 105, 106 

Automobiles, 388 

Bacteria, of air, 76; nitrogen-fixing, 

Baltimore, 131, 286, 385, 401 

Bananas, 339 

Barley, 44, 119, 121, 129, 362 

Barometers, 66 

Barriers, 348 

Bars, 349 

Base-level, 223 

Base-level plain, 227 

Beach, 348 

Birmingham, 386, 403 

Bituminous coal mined in U. S., 377 

Blizzards, 90 

Block mountains, 304 

Bolivia, 44, 102, no, in, 131, 320 

Boot ,and shoe industry, 383, 389 

Borax deposits, 126 

Boston, 344, 376, 401, 404, 405 

Brazil, 53, 104, 271 

Bread fruit, 339 

Hrick, manufacture of, 266 

British Isles, advantages of isolation, 20; 

agriculture in, 121, 361; climate of, 

47, 51, 120, 123, 150; fisheries of, 157; 

rivers of, 246, 271 
Bubonic plague, 109 
Buckwheat, 363 
Buffalo, 279, 282, 286, 289, 302, 390, 

402 
Buffaloes, 327, 328; bones used for 

fertilizer, 170 
Building stones, 175, 377 
Butte. 330, 404 
Gutter, manufacture of, 380, 386 

Caldera, 195 

California, climate of, 77, 79, 118, 120; 

fruit of, 53, 119, 297, 379; gold in, 

175, 181, 378; oil in, 179, 382 
California Trail, 309 
Camels, 107, 331, 332 
Campos, 104 
Canada, 15, 47, 90, 129, 130, 137, 140, 

141, 214, 246, 249, 253, 358, 263, 2S0, 

282, 290, 318,405 



Canals, 285-287; in foreign countries, 

287; influence of, 277, 286; in U. S., 

285-286 
Canning industries, 379, 386 
Canyons, 230; and human activities, 

228 
Caravans, 331, 334, 335 
Carbon dioxide, 29, 30-31, 161, 178; in 

sea-water, 144 
Catskill Mountains, 306, 311, 317 
Cattle, 366-367 
Caverns, 212 

Cement produced in U. S., 176, 377 
Cereals. See Corn, Wheat, etc. 
Changes of level of land, 185-187, 256 
Chemicals and allied products, 384, 388 
Cheese, manufacture of, 380, 386 
Chicago, 279, 281, 282, 302, 328, 380, 

383, 385, 386, 389, 397, 402, 403 
Chile, 105, 119, 121 

China, 80, 109, 122, 165, 166, 242, 243, 
269, 308, 312, 317, 327, 353, 387; 
famines in, 109; Great Wall of, 327; 
isolated development of, 308 

Chinook winds, 90 

Cincinnati, 276, 302, 389, 402 

Circle of illumination, 11,12 

Circulation of air, 72-74 

Cities, air of, 32; on alluvial terraces, 
243; commercial, 401; on deltas, 243; 
fogs of, 62; on Great Lakes, 279, 282, 
402; increasing number and size of, 
399; location of, 3, 399-405; manu- 
facturing, 403; about mines, 315, 403; 
on rivers, 239, 240, 401, 402; in 
tropics, no; types of, 399 

Civil War, Confederate defenses along 
Mississippi, 239; and Great Appa- 
lachian Valley, 173; and Mississippi 
delta, 242; sectionalism leading to, 
364; use of wind-gaps in, 234 

Clays and clay products, 176, 266, 377, 

384, 389 

Cleveland, 279, 282, 302, 383, 386, 390 

Cliff-dwellers, 230 

Cliffs, 347 

Climate, affected by altitude, 77, 79, 
106, 109, 130, 334; affected by ocean 
currents, 150; and cereals, 59, 121, 
127-128, 129; changes of, 31, 79, 254; 
chief factors of, 34; as factor in life of 
plains, 323; and manufacturing in- 
dustries, 383 

Climates, of polar regions, 133-139; of 
temperate zones, 1 13-132; of tropical 



INDEX 



409 



Climates — continued 
regions, 98-112; of the U. S., 118, 
120, 125-128, 130 

Cloudiness, 64, 84 

Clouds, 62-64 

Coal, 176-178; carbon dioxide produced 
by burning of, 30, 178; conservation 
of, 177-178; distribution of deposits, 
176-177; duration of supply in U. S., 
177; and manufacturing, 381; mining 
of, 177, 378; river trade in, 278, 279; 
total amount in U. S., 177; trade on 
Great Lakes, 282 

Coastal Plains, 21, 322; Atlantic, 171, 
302, 324, 392 

Coast-lines, and harbors, 341-356; char- 
acteristics of, 341; importance of, 341 

Cod fisheries, 375 

Coke, 386 

Cold waves, 90 

Colorado Canyon, 230 

Colorado River, 279, 290; delta of, 241 

Columbia River, 279, 287, 376, 397 

Commerce, of American seaports, 352; 
of the desert, 334; difficulties of, in 
tropical countries, 60; of the Great 
Lakes, 279-285; as influenced by 
form of the earth, 6; of Mississippi 
System, 274-279; on the ocean, 140, 
141, 341; and trade- winds, 107; of 
tropical forests, 104, 339; of U. S. 
with other countries, 140, 141 

Commercial cities, 401 

Conduction, 38 

Connecticut Valley, influence on dis- 
tribution of population, 172, 220,392; 
mountains of, 199; terrace towns of, 

243 

Continental climate, of temperate 
zones, 122; in U. S., 125 

Continental shelf, 19, 20 

Continents, comparison of, 24-25; 
grouping of, 20; and ocean basins, 19; 
and oceans, and temperature, 50 

Contour maps, 16-17 

Conservation, of coal, 177-178, 289; of 
forest resources, 373; of ground- 
waters, 210; of iron, 180; of lead, 182; 
of mineral resources, 183; of petrole- 
um, 179; of soils, 168; of waters in 
irrigation, 294-295 

Convection, 38-39 

Copper, 181, 315; mines of Lake 
Superior region, 181, 378; produced in 
U. S., 181, 377 



Coral reefs, 142, 158-159 

Corn, climate for, 59, 80, 121, 128; 
distribution of, 129, 359; and frosts, 
53; production of, 358, 359; uses of, 
360, 368; water needed by, 32, 207 

Corrasion, 217 

Cotton, 170, 171, 325, 363, 358 

Cotton gin, 364 

Cotton manufactures, 60, 364, 382, 387 

"Cow towns," 328 

Crater Lake, 195 

Creep, of soils, 214 

Crops, of chief importance in U. S., 358, 
359; grown in mountains, 313; and 
marine climate, 121; and rainfall, 76, 
80, 119, 128, 129; and relative humid- 
ity, 59; rotation of, 169. See 
Agriculture 

Crustal movements, 185 

Cumberland-Alleghany Plateau, soils of, 

i73 

Cumberland Gap, 234 

Cumberland National Road, 232, 308 

Cycle of erosion, 227 

Cyclones, 83, 85; factors in climate, 79, 
85, 123; height of, 90; movements of, 
85, 89; places of origin, 89; and 
thunder-storms, 95; tropical, 91, 106; 
and weather, 85, 89, 90, 93; of winter 
vs. summer, 89, 90 

Dairy products, 380, 386 

Danube River, 270 

Date palm, 242, 334 

Death Valley, 58, 126 

Deeps, 143 

Deflection of winds, 73, 84 

Degrees, length of, 11 

Delaware River, 273, 286, 302 

Delta, of Hwang-ho, 242; of Mississippi, 
241, 344, 394; of Nile, 242 

Deltas, 241-243, 267, 344-345; and 
commerce, 344-345; floods on, 242; 
lakes on, 243; soil of, 242 

Denver, 403, 404 

Deposition, by streams, 234-243; by 
glacial waters, 266; by glaciers, 257- 
261 ; by ground-water, 212; by waves, 
348; by wind, 202 

Deserts, 3, 330-336; agriculture in, 332, 
334; animals of, 331; commerce of, 
334; life in, 3, 107, 33o~335j plants 
°fi 65, 330; political conditions in, 
335; of snow and ice, 136, 336 

Detroit, 302, 389, 390 



4io 



INDEX 



Dew, 60, 61; in tropics, 103 

Diastrophism, 185, 306 

Dikes, 198 

Distributaries, 242, 351 

Distribution of population, 392 

Doldrums, 74 

Dover harbor, 355 

Drainage basin, 225 

Drift of ocean water, 148 

Drift, glacial, 165, 257 

Driftless area, 253 

Droughts, 80, 129; and irrigation, 291 

Drowned valleys and harbors, 352 

Drowning of streams, 233 

Dry-farming, 65, 173, 329, 399 

Dry winds, 77 

Dunes, 202, 344, 348, 349 

Dust of air, 32, 201 

Earth, axis of, 6, 11; form of, 5, n 
great relief features of, 19; magnet 
ism of, 18; most favored of planets 
5; motions of, 6-8; orbit of, 7; revolu 
tion of, 6-8; rotation of, 6; size of. 6 

Earthquakes, 187-191; causes of, 188 
destruction by, 189; distribution of 
188; and movements of sea- water 
148, 191 

Ecuador, 47, 102, 320 

Egypt, 291,333 

Elbe River, 270 

Electric Power. See Hydro-Electric Power 

England. See British Isles 

Equator, 6; days and nights at, 13 

Equatorial calms, 74, 101, 102 

Equatorial climate, 102-104; and man, 
3, 103, 104 

Equinoxes, 13 

Erie Canal, 281, 286, 287, 308, 401 

Erosion, by glaciers, 255; by ground- 
water, 211, 213; rate of, 218, 219; 
stages of, 225; by rivers, 217; by 
waves, 347; by wind, 201 

Eskimos, 137, 138 

Europe, climate of northwestern, 51-52, 
120, 150; forestry in , 3 1 6-3 1 7 ; general 
features of, 24; glaciation in, 253; 
rivers of, 269-271; trade with U. S., 
140, 141 

Evaporation, 56-57, 58, 64-65 

Fall Line, 273 

Falls, 230; and rapids, and cities, 288, 

402 
Farm animals, value of, 369 



Farm products, value of, 358 

Farming. See Agriculture 

Faulted mountains, 304 

Faulting, 188 

Ferries, and cities, 403 

Fertilizers, 170, 385 

Figs, 242 

Fiords, 256; as harbors, 353 

Fishing industries, 157, 375-376; of 
Arctic peoples, 138, 336; of British 
Isles, 157; conditions favoring, 157, 
375; of Labrador, 129; of New Eng- 
land, 172,375 

Fissure eruptions, 197 

Flatboats, 275 

Flax, 364 

Flood-plains, deposits on, 236; soils of, 
241 

Floods, 80, 131, 237, 242, 262 

Flour and grist mill products, 288, 385 

Fog, 61, 62 

Fogs, about icebergs, 149; in London, 
32, 62; over ocean currents, 152; in 
polar regions, 135 

Food products, 384, 385; of the sea, 157 

Forecasting of weather, 93 

Forest fires, 373 

Forest products, value of, 371 

Forest reserves, 165, 173, 299, 316 

Forest Service, 373, 380 

Forests, conservation of, 373; of equa- 
torial regions, 103, ^37', ev il effects of 
removal, 317; favored by humid cli- 
mate, 121, 123; and irrigation, 298; 
in mountains, 131, 173, 175; petrified, 
79; reclamation of sand areas by, 165, 
204; reduce erosion, 169, 222; repel 
settlers, 397; of U. S., 370; and water 
power, 290 

France, 53, 118, 120, 270, 290, 312, 317, 
352,361,373 

Frosts, 53, 54-55, 61, 119, 129 

Fruits, in irrigated lands, 297; preserv- 
ing of, 379, 386; production of, in 
U. S., 365; production of , near water 
bodies, 53; shipment of perishable, 
94; in sub-tropical climates, 119 

Fur trade, of Great Lakes, 280; in 
mountains, 318 

Furniture, manufacture of, 288, 380, 
387 

Galveston, harbor of, 354; sea-wall, 92; 

storm, 91 
Ganges River, 242, 269, 351 



! 



INDEX 



411 



Geography, definition of, 1 ; divisions of, 
1 ; relations of, 1-3 

Germany, 53, 123, 176, 270, 287, 290, 
312, 314, 316, 361, 373 

Geysers, 210 

Glacial deposits, 257; and stream 
courses, 264 

Glacial erosion, 255 

Glacial period, 252 

Glacial soils, 165, 172, 173, 174, 175, 
265 

Glacial waters, deposits by, 266; de- 
posits of, and early settlements in 
New England, 172 

Glaciers, 247-267; effect on shore-lines, 
256, 261, 344; functions of, 248; 
movement of, 250;. types of, 249 

Glass, 389, 390 

Glucose, 360 

Gold, 181, 377, 378; in Black Hills, 397; 
in California, 175, 181, 397; produc- 
tion in U. S., 377 

Grand Canyon of the Colorado, 228 

Granite, 175, 302, 380 

Grazing, 173, 175, 385, 397; in arid 
U. S., 175; in the Great Plains, 127, 
173, 328, 366; on margins of deserts, 
332; in mountains, 314; in public 
domain, 314; in semi-arid plains, 326, 
327, 328, 329 

Great Britain. See British Isles 

Great Lakes, cities on shores of, 279, 
282, 402; commerce of, 279-285; coal 
trade of, 282; development of steam 
navigation on, 281; early navigation 
of, 280; freight rates on, 268; grain 
trade of, 284; history of, 264; iron ore 
trade of, 282; lumber trade of, 283; 
navigation season on, 246; steel 
freighters on, 284; total shipments on, 
280 

Great Plains, future use of, 329, 366; 
history of, 327; sand dunes of, 165; 
soils of, 173; underground waters of, 
210, 302 

Greenland, glaciers of, 250; settlements 
in, 137; temperatures in, 136 

Ground- water, 205-215; amount of, 
205; conservation of, 210; courses 
followed by, 206; importance of, 207; 
movement of, 206; surface, 205; work 
of, 211 

Guano, 121, 170 

Gulf of Mexico, 85, 355 

Gulf Stream, 149, 152 



Gullies, destroy land, 221; growth of, 220 
Gypsum, 176, 377 

Hail, 95 

Hammerfest, climate of, 134; harbor of, 
152 

Hanging valleys, 256 

Harbors, 350-355; conditions deter- 
mining value of, 350-351, 401; on 
Great Lakes, 279; and ice, 247; im- 
provement of, 354; in rivers, 351, 
352; and tides, 152, 156 

Hawaiian Islands, 105, 194 

Hay, 297, 363 

Health resorts, 44, 118, 131, 317, 404 

Heat of atmosphere, 34, 39; distributed 
by wind, 51; measurement of, 34-35 

Hemp, 364 

High-pressure belts, 69, 72, 73 

Himalaya Mountains, 19, 44, 79, 311 

Holland, 301 

Horses, 368, 369 

Hot waves, 90 

Hot winds, 65 

Hudson River, 153, 272, 302 

Hudson Valley, early population of, 392; 
and growth of New York City, 401 

Humid climate in temperate zone, 123, 
127, 129 

Humid plains of low latitudes, 337 

Humid regions of U. S., 127 

Humidity, 59; and air pressures, 72; 
and crops, 59 

Humus, 160, 373 

Hurricanes, 91-92, 106 

Hwang-ho River, 165, 242, 269 

Hydro-electric power, 231, 288, 289, 
382 

Ice, of polar regions, 135, 136; on rivers, 
246; on seas and lakes, 246; work of, 
246 

Icebergs, 251; dangerous to steamships, 
149 

Igneous rocks, 315 

Imperial Valley, 242 

India, famines in, 80, 109; irrigation in, 
291; lava fields of, 198; monsoons of, 
75, 108; population of, 109, 311; rain- 
fall in, 108; rivers of, 269 

Indians, check expansion of whites, 
394; of Great Plains, 327, 328; of 
southern Appalachians, 31 1 ; of South- 
west, 333 

Indus River, 269 



412 



INDEX 



Industries, location of, 379-383; of the 

u. s., 357-391 

Inland waters and their uses, 268-303 

Insolation, 35-37 

Intermediate zones. See Temperate 
Zones 

Iron, 179-180; conservation of , 180; dis- 
tribution of deposits, 180; estimated 
supply in U. S., 179, 377; in rocks and 
soils, 162 

Iron and steel industries, 282, 384, 386 

Iron ore, importance of location, 378; 
of Lake Superior region, 180, 282, 
315, 380, 386; movement of, 282; 
production of, in U. S., 179, 180 

Irrigable land, area of, 293 

Irrigated land, crops of, 297; popula- 
tion capacity of, 297; value of, 292 

Irrigation, 126, 173, 175, 291-298, 329, 
397; from artesian wells, 210; early 
practice of, in West, 291; in Egypt, 
291; government projects, 295; in 
humid states, 298; in India, 269, 291; 
and National Forests, 298; in semi- 
arid belt of U. S., 173; in sub-tropical 
regions, 119; in tropical regions, 104, 
no 

Islands, from coral reefs, 158; leading 
types of, in ocean, 20; off glaciated 
coasts, 256, 261; of volcanic origin, 
194 

Isobaric maps, 68, 70, 71 

Isobars, 67, 83; courses of , 69-72 

Isothermal maps, 46, 48, 49 

Isotherms, 45, 84; courses of, 50-52 

Italy, 53, 118, 166, 196, 253, 290, 312, 
345 

Japan, 188, 312, 316, 387 

Japan Current, 150, 152 

Java, 98, 99, 102 

Jetties of the Mississippi, 217, 352 

Kaffir corn, 173, 363, 

Kansas City, 277, 302, 328, 380, 385, 

402 
Kaskaskia, 240, 404 
Krakatoa, 196, 201 

Labrador, 128, 129 
Labrador Current, 150 
Laccoliths, 198, 305 
Lagoons, 348; as harbors, 348, 353 
Lake Agassiz, 262; settlement of floor 
of, 263 



Lake Bonneville, 186 

Lake-breezes, 74 

Lakes, on deltas, 243; glacial, 255, 261; 
oxbow, 239; as resorts, 264; as 
sources of water supply, 302 

Land reduction, rate of, 218, 219 

Land-breezes, 74 

Lands, area and height of, 19, 20; best 
uses of, in North America, 174 

Landslides, 189, 214; and movements of 
sea- water, 148 

Latitude, 9; and isotherms, 50 

Lava, 192; intrusions of, 198 

Lava fields, of India, 198; of the North- 
west, 197 

Lead, 182, 397; production in U. S., 
182, 377 

Leadville, Colo., 315, 381, 397 

Leather and its products, 384, 389 

Lemons, 119, 297 

Life, in Antarctic regions, 135-136; in 
Arctic regions, 137, 336; in arid 
plains, 330; in deserts, 3, 107, 330- 
335; in the Great Plains, 327; in 
humid plains of low latitudes, 337; 
in mountains, 309-318; in oases, 334; 
in plains, 324-340; in plateaus, 320; 
in the sea, 156-158; in semi-arid 
plains, 326; in the temperate zones, 
116, 121, 126, 127, 128, 129; in trade- 
wind belts, 107; in the tropical zone, 
100, 101, 103, 104, 107; in well- 
watered plains of middle latitudes, 324 

Lightning, 95 

Limestone, 175; soils from, 164, 171, 173 

Liquors and beverages, 384, 389 

Littoral currents, 346 

Llanos, 104 

Load of streams, 166, 217 

Loess, 165, 173 

London, air of, 32. 62; commerce helped 
by tides, 271; fogs of, 32, 62; harbor 
of, 352 

Longitude, 9; and time, 10 

Los Angeles, 302, 405 

Louisville, 275, 277, 402; tornado, 97 

Lumber and its manufactures, 384, 387 

Lumber trade, of the Lakes, 283; of 
Mississippi System, 278 

Lumbering, 76, 316, 370-373; kinds of 
wood cut, 371; in Lake states, 283, 
372; in mountains, 316; by states, 372 

Macaroni, 128 
Magnetism of earth, 18 



INDEX 



4i3 



Malaria, in tropics, 103; in U. S., 128, 
301 

Malaspina Glacier, 251 

Manchester Ship Canal, 287 

Mantle rock, 160 

Manufacturing cities, 383, 403; of New- 
England, 288, 381 

Manufacturing industries, 378-391; of 
desert people, ^^; factors controlling 
location of, 379; groups of, 384; of 
interior river cities, 276-277; of 
mountaineers, 309, 318; total value 
of products in U. S., 378, 379 

Map projections, 15 

Marble, 176, 380 

Marshes, and flow of streams, 262; 
glacial, 173, 260; reclamation of, 171, 
241, 242, 300 

Marine climate, in high latitudes, 119; 
and crops, 121 

Marl, 171, 262 

Mature topography, 226 

Mean annual temperature, 35 

Meanders of streams, 239 

Meat-packing industry, 328, 380, 385 

Mediterranean climate, 118 

Mercator's projection, 16 

Meridians, 8, 9 

Metal products, 181-182, 381, 384, 388 

Meteors, 28 

Mexico, 22, 44, 240, 320; trade with 
U. S., 140, 141 

Milch cows, 366, 367 

Millet, 363 

Milwaukee, 282, 302, 389 

Mineral fuels, 176 

Mineral industries, distribution of, 377 

Mineral plant foods, 169 

Mineral products, 175; substitution for 
wood, 176; of U. S., 377 

Mineral resources, conservation of, 183 

Mineral springs and waters, 211, 377 

Mining, 126, 311, 330, 376-378; in- 
fluence on distribution of people and 
growth of cities, 315, 330, 397, 403; 
in mountains, 315 

Minneapolis, 288, 302, 386 

Missouri River, 240, 274, 277, 302; 
influence on distribution of popula- 
tion, 394; transportation of sediment 

ty' J . 6 7 . 
Mississippi River, 240, 243, 246, 273- 
279, 286, 290, 302, 352; as a bound- 
ary, 274; delta of, 241, 242; influence 
on distribution of population, 274, 



Mississippi River — continued 

394; traffic on, 279; transportation of 
sediment by, 166, 217 

Mohawk Valley, 272; early population 
of, 392 

Moisture of atmosphere. 56-65 

Monadnocks, 227 

Monsoons, 75, 108-109; and trade on 
Indian Ocean, 75 

Monsoon climate, 108-109 

Monsoon rains, 79, 108, 109 

Montreal, 401, 405 

Moon, 4, 5; and tides, 147, 154-156 

Moraines, 258; use of hilly, 173, 259 

Mosquitoes, 103, 301 

Mt. Everest, 19 

Mountain climate, in middle latitudes, 
130; in the tropics, 109-111 

Mountaineers, industries of, 318; life of, 
309 

Mountains, 22, 304-319; agriculture in, 
311; as barriers, 307, 311; destruction 
of, 306; distribution of, 23, 304; effect 
on precipitation, 77, 79, 106, 131, 334; 
as forest reserves, 316; life in, 309- 
318; mining in, 315; passes in, 232, 
234, 308, 403; as resorts, 131, 317, 
404; settlement of, 311; stock-raising 
in, 314; summer capitals in, 44; 
sunny vs. shady slopes, 44; types 
of, 304; zones of vegetation in, no, 
3i3 

Narrows, 232 
Nashville, 277, 402, 404 
National Forests, 165, 173, 299, 317; 
grazing in, 315; lumbering in, 373; to 
reclaim sandy areas, 165 
National Monuments, 317 
National Parks, 249, 317, 318 
Natural gas, 179; and location of 
industries, 381, 390; produced in 
U. S., 377; waste of, 29, 179 
Natural levees, 237; and early popula- 
tion of Louisiana, 237 
Naval stores, 325, 380 
Navigable streams of U. S., 271 
Navigation, 231, 268-287; affected by 
tides, 152; on canals, 285-287; cities 
on rivers at head of, 401; of Great 
Lakes, 279-285; improvement of, 
_ 287; of rivers, 268-279 
Neap tides, 156 

New England, early industries in, 172, 
383, 388; early population of, 392; 



414 



INDEX 



New England — continued 

fisheries of, 158, 375; manufacture of 
cotton in, 364, 382; manufacturing 
cities of, 288, 381; mountain resorts 
in, 317; rivers of, 272; soils of, 172; 
use of water power in, 288 

New Orleans, 217, 242, 243, 275, 277, 

New York, 380, 382, 383, 397, 403; 
commercial leadership of, 277, 351, 
401; and Erie Canal, 286; harbor at, 
35°> 35 2 > 354; location of, 405; water 
supply of, 302 

Niagara Falls, 289 

Nile River, 268, 269; delta of, 242 

Nitrate deposits, 121 

Nitrogen, 28, 29-30; in sea-wate_r, 144; 
compounds in soil, 29, 170 

Nomads, 104, 326, 332, 333 

North America, area and population in 
tropics, 98; best use of lands of, 174; 
commerce of, 140, 141; general fea- 
tures of, 25; glaciation of, 252 

Northers, 90 

Norway, 51, 121, 134, 137, 256, 314, 
34i 

Oases, 334 

Oats, 128, 129, 362; climate for, 121, 
362; distribution of, 129, 362 

Ocean areas, 20, 98, 113, 142 

Ocean basins, 19; and continents, 19- 
20 

Ocean currents, 145, 148-152; and cli- 
mate, 51, 150; cold, 145, 150; equa- 
torial, 149, 150; and isotherms, 51; 
map of , 151; warm, 145, 150 

Oceans, 140-159; area of, 20, 142; chief 
source of water vapor, 57; depth of, 
19, 143; distribution of, 98, 99, 113, 
114, 115, 141; exploration of, 142; 
ice on, 246; importance of, 140; land 
areas tributary to several, 23; life of, 
156-158; materials of bottom, 142; 
topography of bottom, 143; trade on, 
34i 

Ohio River, 220, 274, 302 

Oil. See Petroleum 

Old topography, 226, 227 

Olives, 119 

Omaha, 302, 328, 380, 385 

Oozes, 142 

Oranges, 119, 297 

Oregon Trail, 220, 309 

Ores, 212, 315; mined in U. S., 377 



Outwash plain, 266 

Oxygen, of the air, 29, 30, 161; in sea- 
water, 144, 156; in soils, 169, 170 
Oyster fisheries, 376 
Ozone, 29 

Packing industry, 328, 380, 385 
Palestine, 2, 166 
Panama Canal, 191, 287, 355 
Paper and printing, 384, 388 
Parallels, 8 

Pastoral tribes, 104, 326, 327, 332 
Pelee, 192, 197 
Peneplains, 227 
Penguins, 136 
Peoria, 277, 389 
Perihelion, 7 
Peru, 77, no, 121 
Petrified wood, 213 

Petroleum, 178-179; and manufac- 
turing, 382; produced in U. S., 179, 

377 
Philadelphia, 273, 286, 302, 352, 355, 

382, 383, 385, 386, 401, 403, 404 
Philippines, 44 
Phosphates, 1 70-1 71; produced in U. 

. S -' 377 

Piedmont alluvial plain, 236 

Piedmont glaciers, 249, 251 

Piedmont Plateau, 21; early population 
of, 392; soils of, 173 

Pig iron produced in U. S., 377 

Piracy of streams, 233 

Pittsburgh, 275, 276, 278, 386, 401 

Plains, 21, 322-340; advantages of, 322; 
classes of, 322; contrasts among, 21, 
323; density of population in, 323; 
life of, 324-340 

Planets, 4, 5 

Plant life, of Antarctic regions, 135; 
of Arctic regions, 137, 336; de- 
pendence on ground-water, 207; in 
deserts, 65, 107, 330; on mountain 
slopes, 107, no, 313; in the sea, 156- 
158; and soil formation, 164; in the 
temperate zones, 119, 121, 126, 127, 
128, 129, 131; in the tropical zone, 
100, 101, 103, 104, 107, no; and 
water vapor of air, 57 

Plateaus, 21, no, 319-320 

Pleasure resorts, 131, 317, 404 

Polar circles, 15 

Polar regions, climate of, ^7, 133-138; 
extent of, 133 

Poles, 6; magnetic, 18; seasons at, 14 



INDEX 



4i5 



Polyps, 157, 158 

Pompeii, 196 

Population, center of, in census years, 
394; distribution of, 208, 392-399; 
engaged in agriculture, 357; factors 
affecting density, 392; maps, 264, 
281, 393, 395, 398, 400; and rainfall, 
76, 399; rural vs. urban, 383, 399; of 
the tropics, 98, no; at various alti- 
tudes, no, 399 

Pork-packing, 385 

Portland cement, 176, 262 

Porto Rico, 92 

Potassium, in soil, 169, 170 

Potatoes, no, 121, 365 

Pottery, manufacture of, by Indians, 

333 

Poultry and eggs, 370 

Prairies, settlement of, 173, 284, 394; 
soils of, 173 

Precipitation, 64, 76; and altitude, 77, 
90, 106, 131, 334; average on lands, 
57; in California, 77, 79; and density 
of population, 399; factors determin- 
ing, 76; and evaporation, 64; on 
mountains, 77, 79, 131; in polar 
regions, 135; in trade- wind zones, 77, 
105; in U. S., 77-79, 124; for the 
world, 78; in zones of westerlies, 77 

Pressure of air, 66; and altitude, 66; 
distribution of, 67; effects on man, 
in; representation of, on maps, 67 

Pygmies, 339 

Pyrenees, 307; people of western val- 
leys, 311 

Quarrying, 376 
Quebec, 405 

Radiation, 38 

Railroads, accidents on, and fogs, 62; 
and cattle industry, 328; competition 
with waterways, 268, 278; develop- 
ment of, 397; freight rates, 268; and 
growth of cities, 402-403; problems 
of, in equatorial regions, 104; pro- 
jected across Sahara, 335; routes of, 
in rugged regions, 228, 309; and 
snowslides, 131; and standard time, 
11; trans- Appalachian, 308; of the 
U. S., 396 

Rain, 64; how disposed of, 205 

Rainbow, 95 

Rainfall, affected by altitude, 77, 90, 
106, 131, 334; and agriculture, 59, 76, 



\ 



Rainfall — continued 

80, 119, 128, 129, 291; annual, of 
world, 78; in the desert, 106, 108, 334; 
distribution of, 77-79; of marine 
climates, 120; of the Mississippi 
Basin, 79, 85; in polar regions, 135; 
and thunder-storms, 95; in trade- 
wind belts, 77, 105; in tropical zone, 
101, 102, 105, 106, 108; of the U. S., 
77-79,85, 124; variation in, 79; and 
winds, 76, 85; in zones of westerly 
winds, 77 

Rapids, 230 

Reclamation, of arid lands, 291-298; 
of lake lands, 262, 297, 301 ; of swamp 
lands, 300-301 

Reclamation Service, 298 

Red clay, 142 

Reefs, 348; coral, 158 

Refrigerator cars, 365, 379 

Reindeer, 336 

Rejuvenation of streams, 233 

Relief features, 19 

Relief maps, 15 

Rhine River, 270; valley, 270, 309 

Rhone River, 270, 352; valley, 309 

Rice, no, 172, 339, 363 

River navigation, 268-279; decline of, 
278; development of, 268, 275; 
present traffic, 278 

River system, 225 

River valleys and human life, 219 

Rivers, as boundaries, 240, 274; com- 
mercial cities on, 239, 401, 402; 
effect of, on salinity of sea- water, 145; 
effect of, on temperature of sea-water, 
146; of foreign countries, 269-271; 
ice of, 246; and shore-lines, 344; tides 
in, 153; of U. S., 271-279; work of, 
215-245 

Rock waste, 160 

Rocky Mountains, as barriers, 309; 
early settlements in, 397; fur trade 
in, 318; and precipitation, 79; soils in, 

174 
Russia, 2, 122, 123, 130, 246, 269, 32:, 

327, 365 
Rye, 44, 59, 121, 129, 363 



Sahara, 59, 77, 106, 107, 202, 333, 334, 

335 
St. Louis, 47, 277, 302, 318, 328, 383, 

389, 402; tornado at, 97 
St. Pierre, 197 
Salmon industry, 376 



4i6 



INDEX 



Salt, 144, 183; deposits of, 126, 144, 
183; and early settlement of Interior, 
183, 394; produced in U. S., 377; of 
sea, 144, 212 

San Francisco, 47, 352, 401; earthquake 
at, 188, 189 

Sand, abrasion by, 201; deposits of, 165, 
202; for making glass, 390; as water 
carrier, 302 

Sand bars, and navigation, 237 

Sandstone, 176; soils from, 164, 171; 
as water bearer, 302 

Satellites, 4 

Saturation of air, 58 

Sea. See Oceans. 

Sea-breezes, 74 

Sea-island cotton, 363 

Sea-level, changes of, 185, 186 

Sea-water, composition of, 144; gases 
in, 144; movements of, 145, 146, 
147-156, 197; temperature of, 145, 146 

Seal fisheries, 137, 158, 376 

Seasons, 12-15, 3 6 ~37, 4i~435 in high 
latitudes, 43; in low latitudes, 42, 
101, 102; in middle latitudes, 41, 116 

Sediment, amount carried to sea, 212, 
217; how carried, 216; of the sea- 
bottom, 142 

Semi-arid climate in temperate zone, 
123, 126 

Semi-arid regions, 126, 173, 326; life in, 
127, 326-329 

Sensible temperature, 58, 100 

Shackleton expedition, 135 

Shale, soils from, 164; as water bearer, 
302 

Sheep, 368 

Shipbuilding, 172, 384, 390 

Shooting stars, 28 

Shore currents, 148 

Shore-lines, and harbors, 341-356; mod- 
ification of, 343 

Siberia, 47, 123, 134, 136, 137, 246 

Sierra Nevada Mountains, climatic 
barriers, 77, 120, 311 

Silk manufacture, 381, 387 

Sills, 198 

Silver, 181, 388, 397; production in U. 

S.,377 
Simoons, 201 
Sirocco, 90 
Slates, 176 
Slavery, in Alabama, 325; and cotton 

culture, 171, 325, 364; favored by 

climate of South, 2, 171 



Slumping, 213 

Smelting industry, 182, 381 

Snoqualmie Falls, 289 

Snow, 246; fields, 45, 135, 247; and 
temperature of air, 45; value of, 54, 
76, no 

Snowfall and altitude, 131 

Snowslides, damage by, 131 

Soil, 160, 161-171; alkaline, 126, 293; of 
arid regions, 126, 293; classes of, 164; 
conservation of, 168; enrichment of, 
170; evils resulting from erosion of, 
167; factors determining fertility, 171; 
and frost, 53; human responses to, 
324; importance to man, 161; making 
of, 161-164; plant foods in, 169-171; 
prevention of erosion of, 168; pro- 
duced from volcanic materials, 193; 
provinces in U. S., 1 71-175; of re- 
claimed swamps, 300; removal of, 
166-169; waste of, 167 

Solar system, 4 

Solstices, 7, 13, 36, 41 

''Soo Canal," 282 

South America, area and population in 
temperate zone, 113; area and popula- 
tion in tropics, 98; distribution of 
population in, in; general features 
of, 25; rivers of, .271; trade with U. S., 
140, 141 

South Pass, 309 

Spain, 307 

Spanish Trail, 228 

Spits, 349 

Spring tides, 155 

Springs, 208, 301 

St. Anthony's Falls, 288 

Standard time, 11 

Steamboat trade on Mississippi, centers 
of, 276 

Steamboats, 275, 281, 284, 341; losses 
of, 237 

Steamship routes, vary with seasons, 149 

Steamships, lost at sea, 62, 94, 149 

Stock-raising, in mountains, 314; in the 
early western settlements, 274; on 
the Great Plains, 327, 328, 329 

Storms, 81, 83; destruction by, 91-92, 

96, 97 
Streams, accidents to, 233; as boun- 
daries, 240, 274; deposition by, 234; 
and distribution of population, 394; 
importance of, in history of U. S., 
273; meanders of, 239; as sources of 
water supply, 302; work of, 215-24- 



INDEX 



4i7 



Submerged valleys, 143 

Subsoil, 160 

Sub-tropical climates, 117; crops of, 119 

Sudan, 104, 107, 335 

Suez Canal, 282, 355 

Sugar, 366, 382 

Sugar-beet, 297, 366 

Sugar-cane, no, 366 

Sun, apparent motion of, 14; heat of, 

as source of power, 106; nature of, 4; 

source of heat of atmosphere, 34; 

and tides, 147, 155-156; worship of, 

108 
Sunshine, and cloudiness, 64 
Sunstrokes, 58, 90, 100 
Swamps, reclamation of, 171, 241, 300- 

301 
Swine, 368, 369 
Switzerland, 44, 249, 250, 290, 310, 311, 

312,314, 316 

Talus, 163 

Tanning industry, 389 

Temperate zone, northern, seasons in, 
116, 122; temperature range in, 116, 
122 

Temperate zones, area of land in, 113; 
climate of, 1 13-132; extent of, 113; 
population of, 113, 114 

Temperature, and air pressure, 67; and 
altitude, 44; changes and rock-split- 
ting, 162, 163; daily range of, 52; 
distribution of, 37-40; effect of snow 
on, 45, 54, 76; and evaporation, 58; 
of land and water, 40, 50; maximum, 
35; minimum, 35; modified by ocean 
currents, i5o;inpolarregions, 133, 135, 
136; range of, 47, 52, 54; representa- 
tion of, on maps, 45; of the sea, 145; 
seasonal range of, 54; in temperate 
zones, 115, 118, 120, 122, 125, 130; in 
tropical zone, 99-100, 102, 103, 105 

Terraces, alluvial, 243; of drift, 266; 
wave-cut, 347 

Terracing, for agriculture, 168, 312 

Textile manufactures, 60, 384, 387 

Thermometers, 34-35 

Thunder-storms, 95, 102 

Tidal water power, 156 

Tides, 148, 152-156, 271 

Till, 257 

Timber-line, 131, 313 

Tobacco, 170, 172, 365 

Tobacco products, 384, 390 

Tornadoes, 8s, 96 



Trade-wind climate, 77, 105-108; and 
life, 107 

Trade-winds and commerce, 107 

Tree-line, 313 

Tropical climate, 98-1 1 2 ; characteristics 
of, 98; and disease, 103, 104; and life, 
100, 101, 103; 104, 107; types of, 101 

Tropical forests, animals of, 338; com- 
merce of, 104, 339; life in, 3377339 

Tropical regions, area of land in, 98; 
climate of, 98-112; extent of, 98; 
future of, 112; natives of, 3, 100, 103, 
104, 107, no, in, 337; population of, 
98, no 

Tropics of Cancer and Capricorn, 15 

Truckee Pass, 309 

Tundras, 336 

Turpentine, 325, 380 

Typhoid fever, 207 

Undertow, 148 

United States, cities of, 399-405; 
climates of, 118, 120, 125-128, 130; 
distribution of population in, 392- 
399; effects of glaciation in, 258-266; 
exports from, 140; imports to, 141; 
irrigation in, 291-298; railroads of, 
396; rainfall of, 124; soils in provinces 
of, 1 71-175; water power in, 288- 
290; vaterways of, 271-287; wet 
lands of, 300-301 

Valley system, 225 

Valley trains, 266 

Valleys, as centers of human activity, 
219; changed by glaciers, 255; growth 
of, 220-224; stages in history of, 225 

Vegetables, 297, 365; canning of, 379, 
386 

Vegetation, of Antarctic region, 135; of 
Arctic region, 43, 137, 336; in deserts, 
65, 107, 330; on mountain slopes, 107, 
no, 313; of oases, 334; in the tropics, 
100, 101, 103, 104, 107, itc c ' 
Plant Life 

Vehicles, manufacture of, 3S - 

Veins, 212, 315 

Venezuela, 104 

Vesuvius, iq6 

Volcanic cones, 20, 143, 193-195, 305, 
destruction of, 194 

Volcanoes, 191-197; destructiveness of, 
196; distribution of, 193; number of, 
193; products of, 192; in sea, 20, 143, 
148, 193 



4i8 



INDEX 



Volga River, 270 

Vulcanism, 191-199; causes of, 199 

War of 1812, 242, 272, 286 

Washington, D. C., 404 

Water power, 288-290; afforded by- 
hanging valleys, 256; amount devel- 
oped, 288; distribution in U. S., 289- 
290; furnished by mountain streams, 
121, 248, 256, 319; furnished by tides, 
156; future importance, 289; and 
manufacturing, 288, 381; in other 
countries, 290; of Ottawa Valley, 281 

Water supply, 207, 301-303 

Water table, 205 

Water-gaps, 232 

Water vapor, 29, 31-32, 161; and air 
pressure, 67, 72; circulation of, 57; 
functions of, 56; sources of, 56-57 

Wave-cut terraces, 347 

Waves and wave action, 148, 345, 347, 
348 

Weather Bureau, 53, 75, 81; value of 
work of, 53, 94 

Weather forecasting, 81, 93 

Weather maps, 81, 82, 86, 87, 88; 
interpretation of, 83 

Weathering, 161 

Wells, artesian, 209; and domestic water 
supply, 210, 302; and irrigation, 210; 
pollution of waters of, 207 



West Indies, cyclones of, 91, 92 
Westerly winds, rainfall in zones of , 77 
Whaling industry, 107, 137, 158, 376 
Wheat, no, 119, 127, 129, 360-362; 
climate for, 59, 121, 128; distribution 
of, 128, 129, 361; production of, 361 
Whiskey, 360, 389 
Wills Creek, narrows of, 232, 403 
Wind, 72; velocity of, 75, 84, 87; work 

of, 201-205 
Wind-zones, 73-74 
Wind-gaps, 234 

Winds, 72-76; causes of, 72, 74; deflec- 
tion of, 73, 84; and distribution of 
temperature, 51; easterly, 74; and 
evaporation, 58; hot, 65; importance 
of, 72; and movements of sea- water, 
147; periodic, 74; planetary, 74; pre- 
vailing, 74; and rainfall, 76, 77; 
trades, 74, 101, 105; westerlies, 73 
Wine, manufacture of, 379, 389 
Wood-pulp, 288, 380 
Wood- working industries, 380 
Wool clip of U. S., 368 
Woolen manufactures, 381, 387 

Yang-tze River, 269 
Yellow fever, 103, 128 
Youthful topography, 226 

Zinc, 182; produced in U. S., 182, 377 



REFERENCE BOOKS 

The following list contains some sixty books on geography and related subjects 
which might well be in a high school library. If a reference library of twenty- 
five books were to be chosen from the list, those which are starred would be sug- 
gested as most suitable. If only ten books were to be chosen, those marked with 
two stars would be suggested. 

Blackwelder and Barrows: Elements of Geology. New York: American Book 
Co., 1911. Price, $1.40. 

Presents briefly the fundamental principles of geology; helpful in answer- 
ing questions involving the relations of physiograph}' and geology. 
Brigham: Commercial Geography. Boston: Ginn and Co., 1911. Price, $1.35. 

Discusses at length wheat, cotton, cattle industries, iron, and coal, deducing 
from these the principles of commercial geography. Of commercial nations 
the United States is treated most fully. Many good maps and diagrams. 
Brigham: Geographic Influences in American History. Boston: Ginn and Co., 
1903. Price, $1.25. 

Traces in a suggestive way the effects of the larger geographic features 
of the United States on many leading events in its history. 
** Chisholm: Handbook of Commercial Geography. New York: Longmans, Green 
and Co., 191 2. (Revised edition.) Price, $4.80. 

A great store of information about commodities of commerce and the 
commercial geography of all countries. Especially valuable for reference. 
Coman: The Industrial History of the United States. New York: The Macmillan 
Co., 1905. Price, $1.60. 

Outlines the growth and expansion of the commerce and industries of the 
United States. 
** Davis: Physical Geography. Boston: Ginn and Co., 1898. Price, $1.25. 

Treats especially the life history of land forms. Excellent for discussion of 
coastal plains, stages of river development, and climatic control of land form-.. 
Day: A History of Commerce. New York: Longmans, Green and Co., 1907. 
Price, $1.75. 

Mainly historical, but traces many relations between earth features and 
the development of commerce since the earliest times. 
Dondlinger: The Book of Wheal. New York: Orange Judd Co., 191 2. Price, 
$2.00. 

An exhaustive discussion of the factors affecting the distribution of the 
world's wheat regions, together with all other aspects of wheat as a crop and 
a commodity of commerce. 
Dutton: Earthquakes. New York: G. P. Putnam's Sons, 1904. Price, $2.00. 

Detailed, scientific treatise, covering the nature of earthquakes, their 
causes, the phenomena associated with them, and the leading features of the 
earthquake regions of the world. 
Geikie, James: Earth Sculpture. New York: G. P. Putnam's Sons, 1898. Price, 
$2.00. 

Devoted entirely to the origin and development of land forms. Especially 
good for the effects of geological structure on topographic forms, and for 
glacial action. 



REFERENCE BOOKS 

* Geikie, Sir A.: Elementary Lessons in Physical Geography. New York: The 

Macmillan Co., 1900. Price, $1.10. 

A simple and entertaining description of the more important aspects of 
physical geography. 
Geikie, Sir A.: Scenery of Scotland. New York: The Macmillan Co., 1901. 
Price, $3 .25. 

Most interesting reading, full of information about processes of weather- 
ing and erosion, and particularly about features due to glaciation. Has a 
good chapter on the influence of physiography on the people of Scotland. 
*Gifford: Practical Forestry. New York: D. Appleton and Co., 1902. Price, 
$1.20. 

Simple, effective statements of the relations of forests to soils and stream 
flow, the factors affecting the distribution of forests, and the industrial im- 
portance of forests. 
**Herbertson: Man and his Work. New York: The Macmillan Co., 1902. 
Price, 60 cents. 

A very suggestive discussion of man's relations to his surroundings. 
Herbertson: Descriptive Geographies: one volume each for North America; 
Central and South America; Europe; Africa; Asia; Australia and Oceanica. 
New York: The Macmillan Co., 1902-1903. Price, 70 to 90 cents per volume. 
Collections of the best descriptions of typical sections of the different 
continents. Interesting and instructive supplementary reading. 
Hogarth: The Nearer East. New York: D. Appleton and Co., 1902. Price, $2. 00. 
A regional study of Balkan Europe, Western Asia, and Egypt; considers 
fully the physiography and climate of these regions, and their relations to the 
life of the people. 
*Holdich: India. New York: D. Appleton and Co., 1905. Price, $2. 50. 

Covers thoroughly every phase of the geography of British India. Espe- 
cially good for the study of life conditions in a monsoon region. 
*Hunt: The Cereals in America. New York: Orange Judd Co., 1908. Price, 

$i.75. 

Excellent for details concerning soil and climatic requirements of cereal 
crops. 
Johnson, E. R.: Ocean and Inland Water Transportation. New York: D. Apple- 
ton and Co., 1906. Price, $1.50. 

Discusses fully the commercial importance of inland waterways and the 
chief problems in their use for navigation. 

* Johnson, W. E.: Mathematical Geography. New York: American Book Co., 

1907. Price, $1.00. 

A standard reference for all matters concerning the form, motions, and 
dimensions of the earth, and for tides and map making. 
Johnstone: Conditions of Life in the Sea. New York: G. P. Putnam's Sons, 

1908. Price, $3.00. 

Describes the plants and animals of the sea, their distribution, and their 
uses by man. Good also for methods of exploration of the sea and the main 
features of the North Atlantic Ocean. 

* Keltie (Editor): The Statesman s Yearbook. New York: The Macmillan Co., 

1863-1911. Price, $3.00. 

An annual publication giving current statistics for all countries. Gives 
also brief statements about government, education, currency, defence, etc., 
for most countries. 
*KiN(;: Fanners of Forty Centuries. Madison, Wis.: Mrs. F. H. King, 191 1. 
Price, $2. so. 

Describes agricultural systems of China and Japan, and tells much about 
the effects of geography on the life of the people. 



REFERENCE BOOKS 

**King: The Soil. New York: The Macmillan Co., 1907. Price, $1.50. 

An exhaustive, but simple, description of soil types, their formation, and 
characteristics. Especially good for discussion of soil moisture. 
**King: Irrigation and Drainage. New York: The Macmillan Co., 1909. Price, 
$1.50. 

Treats in detail the relation of water to plant growth, the soil and climatic 
conditions which make irrigation necessary, the effectiveness of conserving 
water by tillage, and the general problems of irrigation farming. Wet lands 
and their drainage are considered more briefly. 
Kirchoff: Man and Earth. New York: E. P. Dutton and Co., (n.d.p.). Price, 
75 cents. 

A small book with many good examples of man's relations to his surround- 
ings, especially in Great Britain, the United States, Germany, and China. 
Little: The Far East. New York: D. Appleton and Co., 1905. Price, $2.00. 

A regional study of China and Japan along the same lines as Hogarth's 
"The Nearer East" (q.v.). 
Lyde: Man and his Markets. New York: The Macmillan Co., 1901. Price, 
50 cents. 

Good material on many of the larger aspects of commercial geography, 
presented in a new way. 
*Mackinder: Britain and the British Seas. New York: D. Appleton and Co., 
1902. Price, $2.00. 

A comprehensive study of every phase of the geography of the British 
Isles. Especially valuable for the ten chapters tracing the effects of physical 
conditions on the development of the four countries. 
Mead: Story of Gold. New York: D. Appleton and Co., 1906. Price, 75 cents. 
Describes the conditions of occurrence of gold, the methods of mining, the 
chief gold regions of the world, and the importance of gold in industry and 
coinage. 
Milham: Meteorology. New York: The Macmillan Co., 1912. Price, $4.50. 

Embodies the latest results of the investigation of atmospheric phenomena. 
Especially good on atmospheric moisture and irregular winds. 
** Mill (Editor) : The International Geography. New York: D. Appleton and Co., 

1905. Price, $3.50. _ 

A handbook giving the main geographical aspects of all countries, by 
seventy authors. 
Mill: The Realm of Nature. New York: Chas. Scribner's Sons, 1892. Price, 
$1.50. 

An elementary and stimulating treatment .of physiography from the 
English viewpoint. Traces the interdependence of the different aspects of 
nature. 
* Moore, W. L.: Descriptive Meteorology. New York: D. Appleton and Co., 
19 10. Price, $3.00. 

A general text, less advanced than Milham (q.v.); especially good for 
methods of weather forecasting. An appendix of 45 valuable charts. 
*Moulton: An Introduction to Astronomy. New York: The Macmillan Co., 

1906. Price, $1.60. 

A clear, comprehensive exposition of modern astronomy. Especially good 
for discussion of the evolution of the solar system, and the planetary relations 
of the earth. 
Newell: Irrigation. New York: T. Y. Crowell and Co., 1906. Price, $2.00. 

Describes in detail the conditions of arid United States, the supplies of 
water, the methods of storing and distributing water, irrigation law, the 
irrigated regions of the West, and the relation of irrigation to crops in the other 
parts of the country. 



REFERENCE BOOKS 

Partsch: Central Europe. New York: D. Appleton and Co., 1903. Price, $2.00. 
Deals mainly with Germany and Austria-Hungary in a manner similar 
to Hogarth's "The Nearer East" (q.v.). 
Russell: North America. New York: D. Appleton and Co., 1904. Price, $2.00. 
Treats in detail the coasts, topography, geology, and climate of the United 
States, and considers less fully the other parts of the continent. Discusses 
also distribution of plant and animal life. 
Russell: Glaciers of North America. Boston: Ginn and Co., 1897. Price, $1.75. 
Same type of book as Russell's "Rivers of North America" (q.v.). 

* Russell: Rivers of North America. New York: G. P. Putnam's Sons, 1898. 

Price, $2. oo. 

An extensive treatment of the characteristics and work of streams. Good 
descriptions of the main river systems of the continent. 
Russell: Volcanoes of North America. New York: The Macmillan Co., 1897. 
Price, $4.00. 

Same type of book as Russell's "Rivers of North America" (q.v.). 
Ries: Economic Geology. New York: The Macmillan Co., 1910. Price, $3.50. 

Explains the formation and distribution of mineral deposits. Much 
information about important regions of mineral production. 
** Salisbury: Physiography: Briefer Course. New York: Henry Holt and Co., 
1908. Price, $1.50. 

A general text which emphasizes physiographic processes and their effects 
on land forms. 
**Semple: Influences of Geographic Environment. New York: Henry Holt and 
Co., 1911. Price, $4.00. 

Deals mainly with human responses to geographic conditions in typical 
environments. Large amount of excellent material for supplementary reading. 
*Semple: American History in its Geographic Conditions. Boston: Houghton, 
Mifflin and Co., 1903. Price, $3.00. 

Traces the influence of geography on United States history. Enriches the 

study of either subject. 

Shaler: Aspects of 'the Earth. New York: Chas. Scribner's Sons, 1889. Price, $2.50. 

A popular account of some of the larger features of earth science. Very 

suggestive on "Caverns and Cavern Life" and on "The Origin and Nature 

of Soils." 

* Shaler: Man and the Earth. New York: Fox, Duffield and Co., 1905. Price, 

$1.50. 

States in an interesting and convincing way man's dependence on the 
resources of the earth, and the need for conserving them. 
Shaler: Nature and Man in America. New York: Chas. Scribner's Sons, 1893. 
Price, $1.50. 

Discusses the influences of environment on man's progress in civilization, 
and especially the effects of the physical features of North America on the set- 
tlement and development of the continent. 
Shaler: TheStory of Our Continent. Boston: Ginn and Co., 1897. Price, 75 cents. 
A short, simple account of the geologic development of North America, 
the present condition of the continent, and of some of the larger effects of 
geography on the people. 
Shaler: Sea and Land. New York: Chas. Scribner's Sons, 1894. Price, $2.50. 
Features of coasts and oceans, with their influences on man. Excellent 
for material on harbors. 
Smith: The Story of Iron and Steel. New York: D. Appleton and Co., 1908. 
Price, 75 cents. 

A non-technical description of the industry and its development, par- 
ticularly in the United States. 



REFERENCE BOOKS 

* Stanford (Publisher) : Compendium of Geography and Travel. Twelve volumes. 
London: Edward Stanford, 1895-1908. Price, $5.50 per volume. 

Volumes for each of the continents, describing their physiography, climate, 
resources, and something of the development of each of their countries. 
Surface: The Story of Sugar. New York: D. Appleton and Co., 1910. Price, 
$1.00. 

Discusses the natural conditions required for sugar cane and sugar beets, 
the sugar regions of the world, the processes of manufacturing sugar, and its 
commercial importance. 
Taylor: Australia: Physiographic and Economic. Oxford, Eng. : Clarendon Press, 
191 1. Price, 90 cents. 

An excellent analysis of the natural regions of Australia and their relations 
to the economic development of the country. Many good maps and diagrams. 
Tower: The Story of Oil. New York: D. Appleton and Co., 1909. Price, 
$1.00. 

An account of the development of the petroleum industry, mainly in the 
United States. Discusses also commercial and industrial importance of 
petroleum products. 
** Van Htse: Conservation of Natural Resources in the United States. New York: 
The Macmillan Co., 1910. Price, $2.00. 

Considers our resources in minerals, forests, waters, and lands; the ways 
in which their use now involves needless waste; and the remedies which 
should be adopted to check these wastes. Outlines the recent Conservation 
Movement. 
**Ward: Climate. New York: G. P. Putnam's Sons, 1908. Price, $2.00. 

A full description of all the important types of climate, and of their influence 
on various human activities. 
Warren: Elements of Agriculture. New York: The Macmillan Co., 1910. Price, 
$1.10, 

Discusses the conditions of plant growth, the mineral plant foods, the 
raising of the chief farm crops and of live stock, and the problems of farm 
management. 
*Widtsoe: Dry Farming. New York: The Macmillan Co., 1911. Price, 
$1.50. 

Explains the principles of conserving soil moisture, the water requirements 
of different crops, the conditions in regions of scanty rainfall, and states what 
can be done to reclaim these regions for agriculture. 
Willis: Agriculture in the Tropics. Cambridge, Eng.: Cambridge University 
Press, 1909. Price, $2.50. 

States concisely the relations of soil, climate, and labor to farming in 
tropical lands, with accounts of the chief tropical crops. Examples drawn 
mainly from Ceylon and India. 



GOVERNMENT PUBLICATIONS 

Much supplementary material may be found in government publications, 
some of which are noted below, with the addresses from which they may be ob- 
tained. Lists of government publications on different topics, as geography, may 
be obtained by addressing: The Superintendent of Public Documents, Washington, 
D. C. 

Bureau of the Census: Reports and Bulletins of^ the Census. These furnish 
statistical and other data concerning population, industries, etc., in the 
United States. Address: The Director, Bureau of the Census, Washington, 

P. c. 



REFERENCE BOOKS 

Department of Agriculture: (i) Yearbook of the Department of Agriculture. 
An annual publication containing detailed statistics of agriculture for the 
United States and general statistics for foreign countries. Also has special 
articles bearing on farm industries. Obtainable through local representatives 
in Congress. (2) List of Publications. A monthly circular giving titles of 
current publications of the Department, including Bulletins and Circulars of 
the Forestry Service, and publications of the Weather Bureau. Address : 
The Editor and Chief, Division of Publications, Dept. of Agriculture, Wash- 
ington, D. C. 

U. S. Geological Survey: (i) Topographic maps of many parts of the country; 
(2) Mineral Resources of the United States, an annual publication; (3) Annual 
Reports; (4) Professional Papers; (5) Bulletins; and (6) Water Supply and 
Irrigation Papers. Many of the above contain much supplementary material 
for work in geography. The Press Bulletins of the Survey are leaflets issued 
at frequent intervals, which contain current items of interest, especially in 
regard to economic aspects of the work of the Bureau. Address : The Director, 
U. S. Geological Survey, Washington, D. C. 

Department of Commerce and Labor: (i) Monthly Summary of Commerce and 
Finance; (2) Commerce and Navigation of the United States; and (3) Com- 
mercial Relations of the United States. These contain elaborate statistical 
data concerning the foreign commerce of the country. The last named, an 
annual volume, discusses our trade with each foreign country. The volume 
on Commerce and Navigation (annual) gives statistics by countries, com- 
modities, and ports of entry or shipment. Address: The Secretary, Depart- 
ment of Commerce and Labor, Washington, D. C. 



MAGAZINES 

The geographical magazines noted below are important helps to students 
and teachers of geography: 
Bulletin of the American Geographical Society. New York: Broadway and 156th 

Street. $5 per year. 
Geographical J our nal. London: Royal Geographical Society. 27 s. per year. 
Journal of Geography. Madison, Wis.: University of Wisconsin.- $1 .00 per year. 
National Geographic Magazine. Washington, D. C: 16th and M Streets. N. W. 

$2 . 50 per year. 
Scottish Geographic Magazine. Edinburgh: Royal Scottish Geographical Society. 

18 s. per year. 



a 



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PHYSICAl 




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MAP OF THE 




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Plate IV. 


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EXPLANATION OF COLORS 








Above 6000 feet 
3000 to 6000 feet 
1500 to 3000 feet 
600 to 1500 feet 
Sea Level to 600 feet 


^^ 


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Depression below Sea Level 


^\(i^4^Si\i 


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Sea depths below 100 fathoms 
colored in darker blue 






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► »«[ (► fcAKTHC'lOWSVk'S COMPARATIVE ATIAJ. .ONDC- »f KlE.'Om AM 



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ggS ^ PLATE V. 




fcAL MAP OF AFRICA. 



Plate VI. 




PHYSICAL MAI] 




EXPLANATION OF COLORS 

T Above 6000 feet 

| 3000 to 6000 feet 

1500 to 3000 feet 

600 to 1500 feet 

Sea Level to 600 feet 

B Depression below Sea Level 

Sea depths below 100 fathoms 
colored in darker blue 



00 200 390 400 590 60 

English Statute Miles 

\ 



:» Longitude East 140 from 



Hr o> mi."' 



Ml KLEJOHK <••• 



F AUSTRALIA. 



Plate VII. 




FEB 17 1913 



